Chapter 12 Surveying: Elements and Equipment

This lesson provides an overview of surveying with emphasis on the principles and procedures of basic surveying and the use of various surveying equipment, instruments, and accessories. For you as an engineering tech, accurate surveying is essential because sound decisions in engineering practice depend on the results of your surveys. Surveying is the science of determining the relative positions of points on or near the earth’s surface. These points may be needed to locate or lay out roads, airfields, and structures of all kinds. They may be needed for cultural, hydrographic, or terrain features for mapping, and, in the military, these points may be targets for artillery and mortar fire. The relative horizontal positions of these points are determined from distances and directions measured in the field. Their vertical positions are computed from differences in elevation, which are measured directly or indirectly from an established point of reference or datum. The earliest application of surveying was in establishing land boundaries. Although many surveyors still establish or subdivide boundaries of landed properties, the purposes of surveys have branched out to many other areas.

Courts may call upon surveyors to substantiate locations of objects involved in cases, such as major traffic accidents, maritime disasters, or even murder cases, in which direction and distance have a bearing. Surveying continues to play an extremely important role in many branches of engineering. Today, surveys are used to map the earth above and below; for navigational charts used in the air, on land, and at sea, and for certain tasks in geology, forestry, archeology, and landscape architecture. As a surveyor, you submit survey results before, during, and after planning and construction of advanced base structures, bridges, roads, drainage works, pipelines, and other types of conventional ground systems. In addition, an engineering tech assigned to an oceanographic unit may be involved in hydrography to a great extent, establishing an offshore triangulation network, depth sounding, and mapping. Again, though these surveys are for various purposes, the basic operations are the same— they involve measurements and computations, fieldwork, and office work.

When you have completed this lesson, you will be able to:

1. Describe the different classifications of surveying.
2. Describe the different types of surveys.
3. Describe the different types of surveying operations.
4. Describe the purpose and uses of basic surveying instruments.
5. Describe the purpose and uses of field equipment.
6. Identify field supplies needed for surveying operations.

Contents

1.0.0 Classification of Surveying

2.0.0 Types of Surveys

3.0.0 Types of Surveying Operations

4.0.0 Basic Surveying Instruments

5.0.0 Field Equipment

6.0.0 Field Supplies

Summary

Review Questions


1.0.0 CLASSIFICATION of SURVEYING

Generally, surveying is divided into two major categories: plane and geodetic surveying.

1.1.0 Plane Surveying

PLANE SURVEYING is a process of surveying in which the portion of the earth being surveyed is considered a plane. The term is used to designate survey work in which the distances or areas involved are small enough that the curvature of the earth can be disregarded without significant error. In general, the term plane surveying applies to surveys of land areas and boundaries (land surveying) in which the areas are of limited extent. For small areas, precise results may be obtained with plane surveying methods, but the accuracy and precision of such results will decrease as the area surveyed increases in size. To make computations in plane surveying, you will use formulas of plane trigonometry, algebra, and analytical geometry. A great number of surveys are of the plane surveying type. Surveys for the location and construction of highways and roads, canals, landing fields, and railroads are classified under plane surveying. Considering that an arc of 10 mile is only 0.04 greater that its subtended chord, that a plane surface tangent to a spherical arc departs only about eight inches at one mile from the point of tangency, and that the sum of the angles of a spherical triangle is only 1 sec greater than the sum of the angles of a plane triangle for an area of approximately 75 square miles on the earth’s surface, it is reasonable to consider the errors caused by the earth’s curvature only in precise surveys of large areas. In this training manual, we will primarily discuss plane surveying rather than geodetic surveying.

1.2.0 Geodetic Surveying

Geodetic surveying is a process of surveying in which the shape and size of the earth are considered. This type of survey is suited for large areas and long lines and is used to find the precise location of basic points needed for establishing control for other surveys. In geodetic surveys, the stations are normally long distances apart, and this type of surveying requires more precise instruments and surveying methods than does plane surveying. The shape of the earth is thought of as a spheroid, although in a technical sense, it is not really a spheroid. In 1924, the convention of the International Geodetic and Geophysical Union adopted 41,852,960 feet as the diameter of the earth at the equator and 41,711,940 feet as the diameter at its polar axis. The equatorial diameter was computed on the assumption that the flattening of the earth caused by gravitational attraction is exactly 1/297. Therefore, distances measured on or near the surface of the earth are not along straight lines or planes, but on a curved surface. Hence, computation of distances in geodetic surveys make allowances for the earth’s minor and major diameters, from which a spheroid of reference is developed. The position of each geodetic station is related to this spheroid. The positions are expressed as latitudes (angles north or south of the Equator) and longitudes (angles east or west of a prime meridian) or as northings and castings on a rectangular grid. The methods used in geodetic surveying are beyond the scope of this training manual. 

 

Test Your Knowledge

1. In surveying, the relative horizontal positions of points are determined in relationship to which of the following elements- measured in the field?

A. Only from distances
B. Only from directions
C. From either distances or directions
D. From both distances and directions

2. When is a survey considered to be a geodetic survey?

A. When the earth’s curvature must be considered
B. When the surface surveyed is water
C. When the data from the survey will be used for mapping
D. When the survey is either a ground or an aerial survey

 

2.0.0 TYPES of SURVEYS

Generally, surveys can be classified by their functions. Functionally, surveys are classed as construction, topographic, route, and special. Special surveys, such as photogrammetry, hydrography, and property surveys, are conducted either with special equipment or for a special purpose. Some of the types of surveys that you may perform as an engineering tech are discussed in the following paragraphs.

2.1.0 Construction Surveys

Construction surveys (sometimes called engineering surveys) obtain data essential for planning, estimating, locating, and layout for the various phases of construction activities or projects. This type of survey includes reconnaissance, preliminary, location, and layout surveys. The objectives of engineering or construction surveying include the following:

  1. Obtaining reconnaissance information and preliminary data engineers require for selecting suitable routes and sites and for preparing structural designs
  2. Defining selected locations by establishing a system of reference points
  3. Guiding construction forces by setting stakes or otherwise marking lines, grades, and principal points and by giving technical assistance
  4. Measuring construction items in place for preparing progress reports
  5. Dimensioning structures for preparation of as-built plans

All of the above objectives are called engineering surveys by the American Society of Civil Engineers (ASCE), and the term “construction survey” is applied to the last three objectives only. The Army Corps of Engineers, on the other hand, generally applies the term “construction surveying” to all of the objectives listed above. Engineering and/or construction surveys, then, form part of a series of activities leading to the construction of a man-made structure. The term “structure” is usually confined to something, like a building or bridge, built of structural members. It is used here in a broader sense, however, to include all man-made features, such as graded areas; sewer, power, and water lines; roads and highways, and waterfront structures. Construction surveys normally cover areas small enough to use the plane surveying methods and techniques.

2.2.0 Topographic Surveys

The purpose of a topographic survey is to gather survey data about the natural and man-made features of land, as well as its elevations. From this information, a three-dimensional map may be prepared. You may prepare the topographic map in the office after collecting the field data or prepare it right away in the field by plane table. The work usually consists of the following:

  1. Establishing horizontal and vertical control that will serve as the framework of the survey
  2. Determining enough horizontal location and elevation (usually called side shots) of ground points to provide enough data for plotting when the map is prepared
  3. Locating natural and man-made features that may be required by the purpose of the survey
  4. Computing distances, angles, and Elevations
  5. Drawing the topographic map Topographic surveys are commonly identified with horizontal and/or vertical control of third and lower-order accuracies.

2.3.0 Route Surveys

Route surveys are those conducted for the location and construction of lines of transportation or communication that continue across country for some distance, such as highways, railroads, open-conduit systems, pipelines, and power lines. Generally, the preliminary survey for this work takes the form of a topographic survey.

In the final stage, the work may consist of the following:

  1. Locating the center line, usually marked by stakes at 100 feet intervals called stations
  2. Determining elevations along and across the center line for plotting profile and cross sections
  3. Plotting the profile and cross sections and fixing the grades
  4. Computing the volumes of earthwork and preparing a mass diagram
  5. Staking out the extremities for cuts and fills
  6. Determining drainage areas for ditches and culverts
  7. Laying out structures, such as bridges and culverts
  8. Locating right-of-way boundaries and staking out fence lines, if necessary

2.4.0 Special Surveys

As mentioned earlier in this lesson, special surveys are conducted for a specific purpose and with special surveying equipment and methods. A brief discussion of some of the special surveys follows.

2.4.1 Land Surveys

Land surveys (sometimes called cadastral or property surveys) are conducted to establish the exact location, boundaries, or subdivision of a tract of land in any specified area. This type of survey requires professional registration in all states. Presently, land surveys generally consist of the following chores:

  1. Establishing markers or monuments to define and thereby preserve the boundaries of land belonging to a private concern, a corporation, or the government.
  2. Relocating markers or monuments legally established by original surveys. This requires examining previous survey records and retracing what was done. When some markers or monuments are missing, they are reestablished following recognized procedures, using whatever information is available.
  3. Rerunning old land survey lines to determine their lengths and directions. As a result of the high cost of land, old lines are re-measured to get more precise measurements.
  4. Subdividing landed estates into parcels of predetermined sizes and shapes.
  5. Calculating areas, distances, and directions and preparing the land map to portray the survey data so that it can be used as a permanent record.
  6. Writing a technical description for deeds.

2.4.2 Control Surveys

Control surveys provide “basic control” or horizontal and vertical positions of points to which supplementary surveys are adjusted. These types of surveys (sometimes termed geodetic surveys) are conducted to provide geographic positions and plane coordinates of triangulation/ traverse stations and the elevations of bench marks. These control points are further used as references for hydrographic surveys of coastal waters, for topographic control, and for the control of many state, city, and private surveys. Horizontal and vertical controls generated by land (geodetic) surveys provide coordinated position data for all surveyors. Therefore, these types of surveys must use first-order and second-order accuracies.

2.4.3 Hydrographic Surveys

Hydrographic surveys are made to acquire data required to chart and/or map shorelines and bottom depths of streams, rivers, lakes, reservoirs, and other larger bodies of water. This type of survey is also important for navigation and the developing water resources for flood control, irrigation, electrical power, and water supply. LIke other special surveys, hydrographic surveys make use of several types of electronic and radio-acoustical instruments. These special devices are commonly used to determine water depths and the location of objects on the bottom by a method called taking soundings. A surveyor takes soundings by measuring the time required for sound to travel downward and reflect back to a receiver aboard a vessel.

Test Your Knowledge

3. Reestablishing an old property boundary from missing requires what kind of survey?

A. Topographic
B. Construction
C. Route
D. Land

4. Gathering information needed to prepare as-built drawings for a completed project requires what kind of survey?

A. Topographic
B. Construction
C. Route
D. Land

5. Gathering data about the natural and man-made features of the land requires what kind of survey?

A. Topographic
B. Construction
C. Route
D. Land

 

3.0.0 TYPES of SURVEYING OPERATIONS

The practice of surveying actually boils down to fieldwork and office work. Field work consists of taking measurements, collecting engineering data, and testing materials. Office work includes computation and drawing the necessary information for the purpose of the survey.

3.1.0 Fieldwork

Fieldwork is of primary importance in all types of surveys. To be a skilled surveyor, you must spend a certain amount of time in the field to acquire needed experience. This training manual will help you understand the theory behind surveying, instruments and their uses, and surveying methods. However, proficiency in actual surveying, as in other professions, depends largely upon the duration, extent, and variety of experience. Develop the habit of studying a problem thoroughly before going into the field. Know exactly what is to be done, how to do it, and the instruments and materials necessary to do it. Developing speed and consistent accuracy in all your fieldwork is essential. This means that you will need practice in handling the instruments, taking observations, keeping field notes, and planning systematic moves. Do not accept any measurement as correct without verification. Whenever possible, verify using a method different than that used in the original measurement. Ensure that the precision of your measurements are consistent with the accepted standard for the survey. Fieldwork also includes adjusting the instruments and caring for field equipment. Do not attempt to adjust any instrument unless you understand the workings or functions of its parts. Instrument adjustments in the early stages of your career require close supervision from a senior engineering tech.

3.1.1 Collection of Engineering Data

Collecting engineering data is part of Seabee surveying. Engineering data is any information essential for efficient construction. Most of your fieldwork, such as running a traverse, leveling, and determining cuts and fills, may be classified under this category. However, compiling these field measurements and converting them into a common medium of value to the engineer requires skill you can only attain through experience. Although all planning and organization is generally handled by the engineering officer or by a senior engineering tech, the actual collection of engineering data will generally be delegated to  12-8 you; hence, it is to your advantage to understand the procedures early on. This job may require combination of fieldwork and office work. If information of the same quality can be found in sources other than actual fieldwork, do not hesitate to use them. If necessary, use spot checks to verify certain points, depending on the source.

Each project requires the study of a different set of engineering data, so the engineering officer or the senior engineering techs must devise a workable method of compilation for each particular project. The compiled data must be complete in all respects required by the project and the compilation completed with sufficient lead time. Generally, a separate folder for each project is maintained and labeled. Some of the engineering data that may be considered for many projects are as follows:

3.1.2 Factors Affecting Fieldwork

The surveyor must constantly be alert to the different conditions encountered in the field. Physical factors, such as terrain and weather conditions, affect each field survey to varying degrees. Fog or mist can limit the ability to take telescope measurements. Swamps and flood plains under high water can impede taping surveys. Sights over open water or fields of flat, unbroken terrain create ambiguities in measurements taken with microwave equipment. The lengths of light-wave distance in measurements are reduced in bright sunlight. Generally, reconnaissance will predetermine the conditions and alert the survey party to the best methods and the rate of progress to expect.

Technical readiness is another factor affecting fieldwork. As you gain experience in handling various surveying instruments, you can shorten survey time and avoid errors that would require resurvey.

The purpose and type of survey are primary factors determining accuracy requirements. First-order triangulation, which becomes the basis or “control” of future surveys, is made to high-accuracy standards. Cuts and fills for a highway survey, on the other hand, have much lower accuracy standards. Some construction surveys require computing normally inaccessible distances. Compute the distance by means of trigonometry, using the angles and the one distance that can be measured. You must make the measurements to a high degree of precision to maintain accuracy in the computed distance. In simple terms, the purpose of the survey determines the accuracy requirements. The required accuracy, in turn, influences the selection of instruments and procedures. For instance, comparatively rough procedures can be used in measuring for earthmoving, but grade and alignment of a highway have to be much more precise. Each increase in precision also increases the time required to make the measurement, since you must take greater care and more observations.

There is always a slight degree of error in survey measurements. No measurement is ever exact. The errors can be systematic or accidental and are explained later in the lesson. Survey measurements are also subject to mistakes. These occur most commonly from misunderstanding of the problem, poor judgment, confusion on the part of the surveyor, or simple oversight. By working out a systematic procedure, the surveyor will often detect a mistake when an operation seems out of place. That procedure will be an advantage in setting up the equipment, making observations, recording field notes, and making computations.

Survey speed is not the result of hurrying; it is the result of saving time through the following factors:

  1. The skill of the surveyor in handling the Instruments
  2. Intelligent planning and preparation of the work
  3. Making only those measurements that are consistent with the accuracy requirements

Experience is of great value, but in the final analysis, it is the exercise of common sense that makes the difference between a good surveyor and an exceptional surveyor.

3.1.3 Field Survey Parties

The size of a field survey party depends upon the survey requirements, the equipment available, the method of survey, and the number of personnel needed to perform the tasks required. The Seabees commonly use three types of field survey parties: level party, transit party, and stadia party.

3.1.3.1 Level Party

The smallest leveling party consists of two people: an instrumentman and a rodman. In this type of organization, the instrumentman acts as note keeper. The party may need another recorder and one or more extra rodmen to improve the efficiency of the leveling operations. Having additional rodmen eliminates the waiting periods while one person moves from point to point, and an additional recorder allows the instrumentman to take readings as soon as the rodmen are in position. When leveling operations take place alongside other control surveys, the leveling party may become part of a combined party with personnel assuming dual duties, as the workload requires or the party chief directs.

3.1.3.2 Transit Party

A transit party consists of at least three people: an instrumentman, a head chainman, and a party chief. The party chief is usually the note keeper and may double as rear chainman, or there may be an additional rear chainman. The instrumentman operates the transit; the head chainman measures the horizontal distances; and the party chief directs the survey and keeps the notes.

3.1.3.3 Stadia Party

A stadia party consists of at least three people: an instrumentman, a note keeper, and a rodman. However, if the distance between the points is great, the party should include a second rodman so that one can proceed to a new point while the other holds the rod on the point being observed. The note keeper records the data called off by the instrumentman and makes the sketches required.

3.1.4 Field Notes

Field notes are the only record left after the field survey party departs the survey site. If these notes are not clear and complete, the field survey is of little value. It is therefore necessary that your field notes contain a complete record of all of the measurements made during the survey and that they include, where necessary, sketches and narrations to clarify the notes. The following guidelines apply.

3.1.4.1 Lettering

All field notes should be lettered legibly. The lettering should be freehand vertical or slanted Gothic style, as illustrated in basic drafting. A fairly hard pencil or a mechanical lead holder with a 3H or 4H lead is recommended.

3.1.4.2 Format

Notes must be made in the regular field notebook and not on scraps of paper for later transcription. Record separate surveys on separate pages or in different books. Mark the front cover of the field notebook with the name of the project, its general location, the types of measurements recorded, the designation of the survey unit, and other pertinent information.

The inside front cover should contain instructions for the return of the notebook, if lost. Reserve the right-hand pages as an index of the field notes, a list of party personnel and their duties, a list of the instruments used, dates and reasons for any instrument changes during the course of the survey, and a sketch and description of the project.

Throughout the remainder of the notebook, clearly indicate the beginning and ending of each day’s work. Where pertinent, also record the weather, including temperature and wind velocities. To minimize recording errors, someone other than the recorder should check and initial all data entered in the notebook.

3.1.4.3 Recording

Field note recording takes three general forms: tabulation, sketches, and descriptions. Any or all of these forms may be combined, when necessary, to make a complete record.

In tabulation, the numerical measurements are recorded in columns according to a prescribed plan. Spaces are also reserved to permit necessary computations.

Sketches add much to clarify field notes; use them liberally when applicable. You may draw them to an approximate scale or exaggerate important details for clarity. A small ruler or triangle can aid in making sketches. Add measurements directly on the sketch or keyed in some way to the tabular data. An important requirement of a sketch is legibility. See that the sketch is drawn clearly and is large enough to easily understand.

Tabulation, with or without added sketches, can also be supplemented with descriptions. The description may be only one or two words to clarify the recorded measurements, or it may be a lengthy narrative if it is to be used at some future time to locate a survey monument.

Erasures are not permitted in field notebooks. Line out individual numbers or lines recorded incorrectly and insert the correct values. Neatly cross out pages to be rejected and reference them to their substitutes. This procedure is mandatory since the field notebook is the book of record and is often used as legal evidence. Use standard abbreviations, signs, and symbols in field notebooks. If there is any doubt as to their meaning, give an explanation in the form of notes or legends.

3.2.0 Office Work

Office work in surveying consists of converting the field measurements into a usable format. The conversion of computed, often mathematical, values may be required immediately to continue the work, or it may be delayed until completion of a series of field measurements. Although these operations are performed in the field during lapses between measurements, they can also be considered office work. Such operations are normally done to save time. Special equipment, such as calculators, conversion tables, and some drafting equipment, are used in most office work. In office work, converting field measurements (also called reducing) involves computing, adjusting, and applying a standard rule to numerical values.

3.2.1 Computation

In any field survey operation, measurements are derived by the application of some form of mathematical computation. It may be simple addition of several full lengths and a partial tape length to record a total linear distance between two points. It may be adding or subtracting differences in elevation to determine the height of instrument or the elevation during leveling. Then again, it may be checking angles to ensure that the allowable error is not exceeded. Office computing converts these distances, elevations, and angles into a more usable form. The finished measurements may end up as a computed volume of dirt to be moved for a highway cut or fill, an area of land needed for a Seabee construction project, or a new position of a point from which other measurements can be made. In general, office computing reduces the field notes to either a tabular or graphic form for a permanent record or for continuation of fieldwork.

3.2.2 Adjustment

Some survey processes are not complete until measurements are within usable limits or the measurements have been corrected to distribute accumulated errors. Small errors that are not apparent in individual measurements can accumulate to a sizeable amount. Adjusting is the process of distributing these errors over many points or stations until the effect on each point is reduced enough to put all measurements within usable limits.

For example, assume that 100 measurements were made to the nearest unit for the accuracy required. This requires estimating the nearest one-half unit during measurement. At the end of the course, an error of + 4 units results. Adjusting this means each measurement is reduced 0.04 unit. Since the measurements were read only to the nearest unit, this adjustment would not be measurable at any point, and the adjusted result would be correct.

3.2.2.1 Significant Figures

Significant figures are those digits in a number that have meaning; that is, those values that are known to be exact. In a measured quantity, the accuracy of the measurement determines the number of significant figures. For example, a roughly measured distance of 193 feet has three significant figures. More carefully measured, the same distance, 192.7 feet, has four significant figures. If measured still more accurately, 192.68 feet has five significant figures.

In surveying, the significant figures should reflect the allowable error, or tolerance, in the measurements. For example, suppose a measurement of 941.26 units is made with a probable error of ± 0.03 unit. The ± 0.03 casts some doubt on the fifth digit which can vary from 3 to 9, but the fourth digit will still remain 2. We can say that 941.26 has five significant figures; and from the allowable error, we know the fifth digit is doubtful. However, if the probable error were ±0.07, the fourth digit could be affected. The number could vary from 941.19 to 941.33, and the fourth digit could be read 1, 2, or 3. The fifth digit in this measurement is meaningless. The number has only four significant figures and should be written as such.

The number of significant figures in a number ending in one or more zeros is unknown unless more information is given. The zeros may have been added to show the location of the decimal point; for example, 73200 may have three, four, or five significant figures, depending on whether the true value is accurate to 100, 10, or 1 unit(s). If the number is written 73200.0, accuracy is carried to the tenth of a unit and indicates six significant figures.

When decimals are used, the number of significant figures is not always the number of digits. A zero may or may not be significant, depending on its position with respect to the decimal and the digits. As mentioned above, zeros may have been added to show the position of the decimal point. Study the following examples:

In long computations, carry out the values to one more digit than the result requires. Round off the number to the required number of digits as a final step.

3.2.2.2 Rounding Off Numbers
3.2.2.3 Checking

Computations Most mathematical problems can be solved by more than one method. To check a set of computations, use a method that differs from the original method, if possible. An inverse solution, starting with the computed value and solving for the field data, is one possibility. You can also use the planimeter and the protractor for approximate checking. Use a graphical solution when feasible, especially if it takes less time than a mathematical or logarithmic solution. Always recompute each step that cannot be checked by any other method, and, if possible, another engineering tech should recompute the problem. When an error or mistake is found, the computation should be rechecked before the correction is accepted.

3.2.3 Drafting Used in Surveying

Except for some freehand sketches, drafting in surveying is generally performed by mechanical means; for example lines and surveying symbols are generally drawn with the aid of a straightedge, spline, template, etcetera. The drawings directly related to surveying are maps, profiles, cross sections, mass diagrams, and, to some extent, other graphical calculations. Their usefulness depends upon how accurately you plot the points and lines representing the field measurements. You must adhere to the requirements of standard drawing practices.

When drawing a property map, include the following general information:

Besides the above information, some other items may be required for the map to become a public record. When this is the case, consult the local office of the Bureau of Land Management or the local surveyors’ society for the correct general information requirements to be included in the map to be drawn.

In drawing maps that will be used as a basis for studies, such as those to be used in roads, structures, or waterfront construction, you are required to include the following general information:

Maps developed as a basis for studies are so varied in purpose that general information will be adequate for some, but not all. The engineering technician, when in doubt, should consult the senior engineering tech, the engineering officer, or the operations officer for the information desired in the proposed map. The senior engineering tech or the chief of the field survey party must know all these requirements before actual fieldwork begins.

A map with too much information is as bad as a map with too little information. It is not uncommon to find a map so crowded with information and other details that it is hard to comprehend. If this happens, draw the map to a larger scale or reduce the information or details on it. Then provide separate notes or descriptions for other information that will not fit well, thus causing the appearance of overcrowding. Studying the features and quality of existing maps developed architects and engineers (A & E) agencies will aid you a great deal in your own map drawing.

3.2.4 Orientation Symbol

Every map you draw has to have an orientation symbol (sometimes called the meridian arrows). The symbol representing the direction of the meridian is a needle or feathered arrow pointing north. It must be long enough to be transferred accurately to any part of the map. The full-head arrow represents the true meridian, the half-head arrow the magnetic meridian. If you draw both (Figure 12-1), you must indicate the angle between them. If possible, the top of a map must always be oriented north; however, the shape of the mapped area or the most important features of the project may alter this preference.

 

Figure 12-1 – An orientation symbol.

3.2.5 Kinds of Maps

Maps are classified according to purpose, scale, or type. Maps classified according to purpose include strategic, tactical, and artillery maps; communications, utilities, or soil maps; and maps pertaining to special studies. Those classified according to scale are large-scale, medium-scale, and small-scale. Some of the more common type classifications, such as geographic, planimetric, topographic, hydrographic, special purpose, and photomaps or mosaics, are briefly described in the next several paragraphs.

3.2.5.1 Geographic Maps

A geographic map is a map of a large area, such as a state or country, that shows the location of towns, counties, cities, rivers or streams, lakes, roads, and principal civil boundaries, such as county and state lines. Maps showing the general location of human works, such as the Railroad Map of the United States, the Irrigation Map of Arizona, and the Panama Canal Zone Map, are also classified as geographical maps.

3.2.5.2 Planimetric Maps

These maps show natural or man-made features in a horizontal plane only. They omit relief in any measurable form. A few examples of planimetric maps are property, city layout, site plan, communications, route and distance, and isogonic maps of the magnetic variation lines.

3.2.5.3 Topographic Maps

Maps that depict the natural and man-made features of the earth’s surface in a measurable form, showing both horizontal and vertical positions are called topographical maps. Vertical positions, or relief, are normally represented by contours. A precise topographic map shows surface features so perfectly that it can be used for making an exact three-dimensional model of the area. Such a model is called a relief map.

3.2.5.4 Hydrographic Maps

A hydrographic map shows the shorelines, location and depth of soundings, and often the topographic and other features of lands adjacent to the shorelines. It also shows the locations of both horizontal and vertical control in the area.

3.2.5.5 Special-Purpose Maps

These are maps developed for specific purposes. A preliminary map developed from a preliminary survey of a highway, a location map showing the alignment of the located line, and a right-of-way map showing the boundaries of the right-of-way and the adjacent lands all come under the heading of special purpose maps.

3.2.5.6 Mosaic and Overlays

 

Editor's Note

The procedures described in this section, "Mosaic and Overlays," have been largely replaced with satellite imaging.  I will update this material when information from the appropriate experts becomes available.

The aerial photographic mosaic is constructed from two or more overlapping prints joined so that they form a single picture. Usually, vertical photographs are used to obtain a map-like result; however, oblique photographs may be used, in which case the result is a panorama. The mosaic has become increasingly useful in cartography and related fields since World War I. It can represent large geographic areas with each feature of terrain assuming its natural appearance and approximating its proportionate size. The U.S. Army Topographic Command has developed from mosaics a multicolored map of the entire United States and maps of other countries. The Army calls it a pictomap; this is the type of map that is generally used in a war zone. Aerial photographs may be converted into line maps by the use of overlays. Usually, these are made by tracing the details from the photograph onto transparent paper or vellum and adding such marginal data as desired. This line map may then be reproduced quickly by blueprinting or by lithography (Figure 12-2).

 

Figure 12-2 – An aerial photograph, and a line map made by overlays of that aerial photograph

 

 

Test Your Knowledge

6. When engineering data for a construction project is collected, which of the following items or information should be considered?

A. Climatology in the local area of the project site
B. Availability of labor and materials
C. Accessibility of construction equipment to the project site
D. All of the above

7. Which of the following factors makes the difference between a good surveyor and an exceptional surveyor?

A. The ability to collect data quickly
B. The ability to exercise sound judgment and common sense
C. Consistent accuracy in field work
D. The habit of ensuring that all survey results are verified before acceptance

8. Where in the field notebook should party personnel and their duties be listed?

A. Front cover
B. Inside front cover
C. Right-hand pages

4.0.0 BASIC SURVEYING INSTRUMENTS

4.1.0 Magnetic Compass

Most fieldwork done by an engineering technician (especially at the third- and second-class levels) consists of field measurements and/or computations involving plane surveying of ordinary precision. This section describes the basic instruments, tools, and other equipment used for this type of surveying. Instruments used for more precise surveys will also be described briefly.

Surveying instruments come in various forms, yet their basic functions are similar. A magnetic compass consists principally of a circular compass card, usually graduated in degrees, and a magnetic needle, mounted and free to rotate on a pivot located at the center of the card. The needle, when free from any local attraction (caused by metal), lines itself up with the local magnetic meridian as a result of the attraction of the earth’s magnetic north pole.

The magnetic compass is the most commonly used and simplest instrument for measuring directions and angles in the field. The lensatic compass  is most commonly used for compass courses, map orientation, and angle direction during mortar and field artillery fires.

In addition to this type of compass, there are several others used exclusively for field surveys. The engineer’s transit compass, located between the standards on the upper plate, is graduated from 0° through 360° for measuring azimuths, and in quadrants of 90° for measuring bearings. The Brunton pocket compass (Figure 12-3) is a combination compass and clinometer. It can be mounted on a light tripod or staff, or it may be cradled in the palm of the hand. Other types of compasses can also be found in some surveying instruments such as the theodolite and plane table.

 

Figure 12-3 – A Brunton pocket transit.

4.2.0 Theodolite

A theodolite is essentially a transit of high precision. Theodolites come in different sizes and weights and from different manufacturers. Theodolites may differ in appearance, but their essential parts and operation are basically alike. Some of the models currently available include the WILD (Herrbrugg), BRUNSON, K&E (Keuffel & Esser), and PATH theodolites.

4.2.1 One-Minute Theodolite

The one minute directional theodolite is essentially a directional type of instrument. With this type of instrument, however, you can observe horizontal and vertical angles, as with a transit.

The theodolite (Figure 12-4) is a compact, lightweight, dustproof, optical reading instrument. The scales read directly to the nearest minute or 0.2 mil and are illuminated by either natural or artificial light.

 

Figure 12-4 – The one minute theodolite.

The main or essential parts of this type of theodolite are discussed in the next several paragraphs.

4.2.1.1 Horizontal Motion

The horizontal motion clamp and tangent screw are located on the lower portion of the alidade and adjacent to each other. They are used for moving the theodolite in azimuth. Located on the horizontal circle casting is a horizontal circle clamp that fastens the circle to the alidade. When this horizontal (repeating) circle clamp is in the lever-down position, the horizontal circle turns with the telescope. With the circle clamp in the lever-up position, the circle is unclamped and the telescope turns independently. This combination permits use of the theodolite as a repeating instrument. To use the theodolite as a directional type of instrument, use the circle clamp only to set the initial reading. Set an initial reading of 0°30´ on the plates when you require a direct and reverse (D/R) pointing. This will minimize the possibility of ending the D/R pointing with a negative value.

4.2.1.2 Vertical Motion

Located on the standard opposite the vertical circle are the vertical motion clamp and tangent screw. The tangent screw is located on the lower left and at right angles to the clamp. Using the vertical motion clamp and the tangent screw, the telescope can be rotated in the vertical plane completely around the axis (360°).

4.2.1.3 Levels

The level vials on a theodolite are the circular, the plate, the vertical circle, and the telescope. The circular level is located on the tribrach of the instrument and is used to roughly level the instrument. The plate level, located between the two standards, is used for leveling the instrument in the horizontal plane. The vertical circle level (vertical collimation) vial is often referred to as a split bubble. This level vial is completely built in, adjacent to the vertical circle, and viewed through a prism and 450 mirror system from the eyepiece end of the telescope. This results in the viewing of one-half of each end of the bubble at the same time. Leveling consists of bringing the two halves together into exact coincidence (Figure 12-5).

 

Figure 12-5 – Leveling by bringing two halves together into exact coincidence

The telescope level, mounted below the telescope, uses a prism system and a 450 mirror for leveling operations. Plunging the telescope to the reverse position brings the level assembly to the top.

4.2.1.4 Telescope

The telescope of a theodolite can be rotated around the horizontal axis for direct and reverse readings. It is a 28-power instrument with a short focusing distance of about 1.4 meters. The cross wires are focused by turning the eyepiece; the image, by turning the focusing ring. The reticle has horizontal and vertical cross wires, a set of vertical and horizontal ticks (at a stadia ratio of 1:100), and a solar circle on the reticle for making solar observations. This circle covers 31 minutes of arc and can be imposed on the sun’s image (32 minutes of arc) to make the pointing refer to the sun’s center. One-half of the vertical line is split for finer centering on small distant objects.

The telescope of the theodolite is an inverted image type. Its cross wires can be illuminated by either sunlight reflected by mirrors or by battery source. Adjust the amount of illumination for the telescope by changing the position of the illumination mirror.

4.2.1.5 Tribrach

The tribrach assembly, found on most makes and models, is a detachable part of the theodolite that contains the leveling screw, the circular level, and the optical plumbing device. A locking device holds the alidade and the tribrach together and permits interchanging of instruments without moving the tripod. In a “leapfrog” method, the instrument (alidade) is detached after observations are completed. It is then moved to the next station and another tribrach. This procedure reduces the amount of instrument setup time by half.

4.2.1.6 Circles

The theodolite circles are read through an optical microscope. The eyepiece is located to the right of the telescope in the direct position and to the left in the reverse. The microscope consists of a series of lenses and prisms that bring both the horizontal and the vertical circle images into a single field of View. Degree-graduated scales show the images of both circles as they would appear through the microscope of the one minute theodolite. Both circles are graduated from 0° to 360° with an index graduation for each degree on the main scales. This scale’s graduation appears to be superimposed over an auxiliary that is graduated in minutes to cover a span of 60 minutes (1°). The position of the degree mark on the auxiliary scale is used as an index to get a direct reading in degrees and minutes. If necessary, these scales can be interpolated to the nearest 0.2 minute of arc. The vertical circle reads 0° when the theodolite’s telescope is pointed at the zenith, and 180° when it is pointed straight down. A level line reads 90° in the direct position and 270 in the reverse. The values read from the vertical circle are referred to as zenith distances and not vertical angles (Figure 12-6).

 

Figure 12-6 – Converting zenith distance into vertical angles (degrees).

In the mil-graduated scales (Figure 12-7, the images of both circles are shown as they would appear through the reading microscope of the 0.2-mil theodolite. Both circles are graduated from 0 to 6,400 mils. The main scales are marked and numbered every 10 mils, with the last zero dropped.

 

Figure 12-7 – Vertical angles from zenith distances (mils).

The auxiliary scales are graduated from 0 to 10 roils in 0.2-mil increments. Readings on the auxiliary scale can be interpolated to 0.1 mil. The vertical circle reads 0 mil when the telescope is pointed at the zenith, and 3,200 mils when it is pointed straight down. A level line reads 1,600 roils in the direct position and 4,800 roils in the reverse. The values read are zenith distances.

4.2.2 One-Second Theodolite

The one second theodolite (Figure 12-8) is a precision direction type instrument for observing horizontal and vertical directions.

 

Figure 12-8 – One second Theodolite.

This instrument is similar to, but slightly larger than, the one minute theodolite. The one second theodolite is compact, lightweight, dustproof, optical reading, and tripod-mounted. It has one spindle, one plate level, a circular level, horizontal and vertical circles read by an optical microscope directly to one second (0.002 roil), clamping and tangent screws for controlling the motion, and a leveling head with three foot screws.

The circles are read using the coincidence method rather than the direct method. There is an inverter knob for reading the horizontal and vertical circles independently. The essential parts of a one second theodolite are very similar to those of the one minute theodolite, including the horizontal and vertical motions, the levels, the telescope, the tribrach, and the optical system (Figure 12-9). The main difference between the two types, besides precision, is the manner in which the circles are read.

 

Figure 12-9 –Circle-reading optical system.

To view a circle in the one second theodolite select it by turning the inverter knob on the right standard. The field of the circle-reading microscope shows the image of the circle with lines spaced at 20 second intervals, every third line numbered to indicate a degree, and the image of the micrometer scale on which the unit minutes and seconds are read. The numbers increase in value (00 to 3600) clockwise around the circle. The coincidence knob on the side of, and near the top of, the right standard is used in reading either of the circles. Use the collimation level and its tangent screw to read the vertical circle.

Read the circles of the theodolite by the coincidence method, in which you obtain optical coincidence between diametrically opposite graduations of the circle by turning the micrometer or coincidence knob. When you turn this knob, the images of the opposite sides of the circle appear to move in opposite directions across the field of the circlereading microscope. The graduations can be brought into optical coincidence and appear to form continuous lines crossing the dividing line. An index mark indicates the circle graduations to be used in making the coincidence. The index mark will be either in line with a circle graduation or midway between two graduations. Make the final coincidence adjustment between the graduations in line with the index mark or when this index mark is halfway between the two closest graduations.

4.2.2.1 Horizontal Circle

To read the horizontal circle, turn the inverter or circle-selector knob until its black line is horizontal. Adjust the illuminating mirror to give uniform lighting to both sections of the horizontal circle; then view the micrometer scale through the circle-reading microscope. Focus the microscope eyepiece so that the graduations are sharply defined.

From this point, continue in the following way:

  1. Turn the coincidence knob until the images of the opposite sides of the circle move into coincidence. Turning this knob also moves the micrometer scale.
  2. Read the degrees and tens of minutes from the image of the circle. The nearest upright number to the left of the index mark is the number of degrees (105). The diametrically opposite number (the number ± 180) is 285. The number of divisions of the circle between the upright 105 and inverted 285 gives the number of tens of minutes. You may also use the index for direct reading of the tens of minutes. Each graduation is treated as 20 seconds. Thus, the number of graduations from the degree value to the index mark multiplied by 20 seconds is the value. If the index falls between graduations, add another 10 seconds when reading the tens of minutes directly.
  3. The scale has two rows of numbers below the graduations; the bottom row is the unit minutes and the top row, seconds.
  4. Add the values determined in Steps 2 and 3 above.
4.2.2.2 Vertical Circle

When reading the vertical circle, turn the circle-selector knob until its black line is vertical. Adjust the mirror on the left standard and focus the microscope eyepiece. Continue by:

  1. Using the vertical circle tangent screw to move the collimation level until the ends of its bubble appear in coincidence in the collimation level viewer on the left standard.
  2. Reading the vertical circle and micrometer scale as described before. Be sure to have proper coincidence before taking the reading.

The vertical circle graduations are numbered to give a 00 reading with the telescope pointing to the zenith. Consequently, the vertical circle reading will be 900 for a horizontal sight with the telescope direct and 2700 for a horizontal sight with the telescope reversed.

There are two separate occasions for setting the horizontal circle of the theodolite. In the first case, set the circle to read a given value with the telescope pointed at a target. With the theodolite pointed at the target and with the azimuth clamp tightened, set the circle as follows: Set the micrometer scale to read the unit minutes and the seconds of the given values. Then, with the circle-setting knob, turn the circle until you obtain coincidence at the degree and tens of minutes value of the given reading. This setting normally can be made accurately to plus or minus five seconds. After the circle is set in this manner, determining the actual reading.

In the second case, set the circle to a given angle. When measuring a predetermined angle, first point the instrument along the initial line from which the angle is to be measured and read the circle. Add the value of the angle to the circle reading to determine the circle reading for the second pointing. Set the micrometer scale to read the unit minutes and the seconds of the value to be set on the circle. Then turn the instrument in azimuth and make coincidence at the degrees and tens of minutes value to be set. The predetermined value can usually be set on the circle in this way to plus or minus two seconds.

4.3.0 Precision Level

The self-leveling level has in recent years become standard equipment. These precision instruments are like conventional levels with several additional features.

A precision level is equipped with an extra-sensitive level vial. The sensitivity of a level vial is usually expressed in terms of the size of the vertical angle the telescope must be moved to cause the bubble in the level vial to move from one graduation to the next.

The sensitivity of the level vial on an ordinary level is about 20 seconds. On a precise level, the level vial sensitivity is about two seconds. The telescope level vial on an ordinary transit has a sensitivity of about 30 seconds. The more sensitive the level vial is, the more difficult it is to center the bubble. If the level vial on an ordinary level had a sensitivity as high as two seconds, the smallest possible movement of the level screw would cause a large motion of the bubble.

For this reason, a precise level is usually also a tilting level. On a tilting level, the telescope is hinged at the objective end in order to raise or lower the eyepiece end. The eyepiece end rests on a finely threaded micrometer screw that turns to raise or lower the eyepiece end in small increments. The instrument is first leveled, as nearly as possible, following the typical steps. The bubble is then brought to exact center by the use of the micrometer screw.

4.3.1 Military Level

The military level (Figure 12-10) is a semi-precise level designed for more precise work than the engineer’s level. The telescope is 30-power, 10-inch-long, interior-focusing with an inverting eyepiece and an enclosed fixed reticle. The reticle is mounted internally and cannot be adjusted as in other instruments. It contains cross wires and a set of stadia hairs. The objective is focused by an internal field lens through a rack and pinion, controlled by a knob on the upper right-hand side of the telescope.

 

Figure 12-10 – A military level.

Tilt the telescope and level vial through a small angle in the vertical plane to make the line of sight exactly horizontal just before making the rod reading. The tilting is done by a screw with a graduated drum located below the telescope eyepiece. A cam is provided to raise the telescope off of the tilting device to hold it firmly when you are moving the instrument during the preliminary leveling. An eyepiece, located to the left of the telescope, is used for viewing the bubble through the prism system that brings both ends of the bubble into coincidence.

The level vial is located directly under the telescope, but to the left and below, directly in line with the capstan screws under the bubble viewing eyepiece. The level vial’s sensitivity is 30 seconds per 2-millimeter spacing. A circular bubble that is viewed through a 450 mirror is provided for the first approximate leveling before the long level vial is used. For night work, battery-powered electric illumination lights the long bubble, the reticle, and the circular level. The clamping screw and the horizontal motion tangent screw are located on the right-hand side; the former near the spindle and the latter below the objective lens. The instrument has a three-screw leveling head. The tripod for this level has a non-extension leg to add rigidity and stability to the setup.

4.3.2 Self-Leveling Level

The self-leveling level, also called automatic level, (Figure 12-11) is a precise, time-saving development in leveling instruments. It does away with the tubular spirit level, whose bubble takes a longer time to center as well as reset to its correct position.

 

Figure 12-11 – An automatic level.

The self-leveling level is equipped with a small bull’s-eye level and three leveling screws. The leveling screws, which are on a triangular foot plate, are used to give an approximate center of the bull’s-eye level. The line of sight automatically becomes horizontal and remains horizontal as long as the bubble remains approximately centered. A prismatic device called a compensator makes this possible. The compensator is suspended on fine, nonmagnetic wires. The action of gravity on the compensator causes the optical system to swing into the position that defines a horizontal sight. This horizontal line of sight is maintained despite a slight out of level of the telescope or even when a slight disturbance occurs on the instrument.

4.3.0 Hand Level

The hand level, like all surveying levels, is an instrument that combines a level vial and a sighting device. It is generally used for rough leveling work. In cross-sectional work, for example, terrain irregularities may cause elevations to go beyond the instrument range from a setup. A hand level is useful for extending approximate elevations off the control survey line beyond the limits of the instruments.

For greater stability, both hand levels may be rested against a tree, rod, range pole, or on top of a staff. A horizontal line, called an index line, is provided in the sight tube as a reference line. The level vial is mounted atop a slot in the sight tube in which a reflector is set at a 45° angle. This permits the observer, while sighting through the tube, to see the landscape or object, the position of the bubble in the vial, and the index line at the same time. The distances over which a hand level is sighted are comparatively short; therefore, it provides no magnification for the sighting.

The Abney hand level is more specialized than the Locke type. It has a clinometer for measuring the vertical angle and the percent of grade. The clinometers has a reversible graduated arc assembly mounted on one side. The lower side of the arc is graduated in degrees, and the upper side, in percent of slope. The level vial is attached to the axis of rotation at the index arm. When the index arm is set at zero, the clinometer is used like a plain hand level. The bubble is centered by moving the arc and not the sighting tube as is the case in the plain hand level. Thus, the difference between the line of sight and the level bubble axis can be read in degrees or percent of slope from the position of the index arm of the arc. The 45° reflector and the sighting principle with its view of the landscape, bubble, and index line are the same as in the plain hand level.

 

Test Your Knowledge

9. What part of an engineer’s transit serves the same function as the tribrach of the theodolite?

A. Leveling assembly
B. Lower plate
C. Upper plate
D. Standard

4.4.0 Trimble® 5600 and Terramodel™ Software

The Trimble® 5600 Total Station (Figure 12-12) is designed to support integrated surveying by combining GPS and optical survey data from the field into an electronic file that can used with Trimble office software for processing. Integrated surveying enables you to maximize the best of both surveying techniques for optimal efficiency in the field. 

 

Figure 12-12 – Trimble® 5600 Total Station.

The Trimble Terramodel™ software package (Figure 12-13) allows the import of raw data collected using conventional instruments or the automated total stations and roving GPS receivers to a Windows™ based personal computer. The software provides the capability to view project data as an interactive 3D model, which makes design and processing of data from a survey extremely efficient. Possessing CAD functions the Terramodel™ software enables you to perform survey and CAD tasks all with one package.

 

Figure 12-13 – Terramodel™ Screen Example.

 

5.0.0 FIELD EQUIPMENT

 The term field equipment, as used in this training manual, includes all devices, tools, and instrument accessories used in field measurement.

5.1.0 Field Tools

If you are running a survey across rough terrain, the essential equipment you will need includes various types of tools used for clearing the line; that is, for cutting down brush and other natural growth as circumstances require.

Surveying procedures usually permit bypassing large trees. Occasionally, however, it may be necessary to fell one. If heavy equipment is available, an EO may fell the tree with a bulldozer. The next best method is by means of a power-driven chain saw. If no chain saw is available, a one-man or two-man crosscut saw may be.

The machete and brush hook (Figure 12-14) are used for clearing small saplings, bushes, vines, and similar growth. Axes and hatchets are used for felling trees and also for marking trees by blazing. Files and stones are used to sharpen the edges of tools. Hubs, stakes, pipe, and other driven markers are often driven with the driving peen of a hatchet or a single-bit ax.

 

 Figure 12-14 – Standard field tools.

A sledgehammer, however, is a more suitable tool for driving markers. A double-faced, long-handled sledgehammer is swung with both hands. There are also short-handled sledgehammers, swung with one hand. A sledgehammer is classified according to the weight of the head; common weights are 6, 8, 10, 12, 14, and 16 lb. The 8- and 10-lb weights are the most commonly used.

When the ground is too compact or frozen to permit driving wooden stakes and hubs directly, open the way for a stake or hub by first driving in a heavy, conical-pointed steel bar, 10 to 16 inches long, called a bull-point. You can use one of the heavy steel form pins, used to pin down side forms for concrete paving, as a bull-point; however, the pyramidal pavement-breaker bit on a jack hammer (pneumatic hammer used to drive paving breaker bits, stone drills, and the like) makes a better bull-point. Because a jack hammer bit is made of high-carbon steel, it is liable to chip and mushroom when subjected to heavy pounding. Do not use a bull-point with a badly damaged head; to avoid injury to personnel, refinish it by grinding or cutting off before using it.. In searching for hidden markers, you may need a shovel for clearing top cover by careful digging. In soft ground, such as loose, sandy soil, you may prefer to use a square-pointed shovel or a probing steel rod to locate buried markers.

Chipping bituminous pavement off of manhole covers and levering them up may require a pick. Sometimes you will need a crowbar for levering manhole covers. A dip needle or a battery-powered instrument called a pipe finder, similar in principle to a mine detector, helps to locate buried metal markers. These instruments are used in engineering surveys to locate utility pipelines, buried manhole and valve box covers, and the like. You can generally borrow these instruments from the utilities division of the Public Works Department (PWD) of larger shore stations.

5.2.0 Surveying Tapes

Tapes are used in surveying to measure horizontal, vertical, and slope distances. They may be made of a ribbon or a band of steel, an alloy of steel, cloth reinforced with metal, or synthetic materials. Tapes are issued in various lengths and widths and graduated in a variety of ways.

5.2.1 Metallic Tapes

A metallic tape is made of high-grade synthetic material with strong metallic strands (bronze/brass- copper wire) woven in the warped face of the tape and coated with a tough plastic for durability. Standard lengths are 50 and 100 feet.

Some are graduated in feet and inches to the nearest one-fourth inch. Others are graduated in feet and decimals of a foot to the nearest 0.05 feet. Metallic tapes are generally used for rough measurements, such as cross-sectional work, road-work slope staking, side shots in topographic surveys, and many others in the same category. Nonmetallic tapes woven from synthetic yarn, such as nylon, and coated with plastic are available; some surveyors prefer to use tapes of this type. Nonmetallic tapes are of special value to power and utility field personnel, especially when they are working in the vicinity of high voltage circuits.

5.2.2 Steel Tapes

Direct linear measurements of ordinary or more accurate precision require a steel tape. The most commonly used length is 100 feet, but tapes are also available in 50-, 200-, 300-, and 500-feet lengths. All tapes except the 500-foot are band-types, the common band widths being ¼ and 5/16 inch. The 500-tape is usually a flat-wire type.

Most steel tapes are graduated in feet and decimals of feet, but some are graduated in feet and inches, meters, Gunter’s links, and chains or other linear units. From now on, when we discuss a tape, we will be talking about one that is graduated in feet and decimals of a foot unless stated otherwise.

Some tapes, called engineer’s or direct reading tapes, are graduated in subdivisions of each foot. The tape most commonly used, however, is the so-called chain tape, on which only the first foot at the zero end of the tape is graduated in subdivisions; the main body of the tape is graduated only at every one foot mark. A steel tape is sometimes equipped with a reel on which the tape can be wound, although a tape can be, and often is, detached from the reel for convenience.

There are various types of surveying tapes; metallic tape, steel tape on an open reel, steel tape on a closed reel, and special types of low-expansion steel tape, generally called an Invar tape or Lovar tape, used in high-order work.

5.2.3 Invar Tapes

Nickel-steel alloy tapes, known as Invar, Nilvar, or Lovar, have a coefficient of thermal expansion of about one-tenth to one-thirtieth (as low as 0.0000002 per 10F) that of steel. These tapes are used primarily in high-precision work. They must be handled in exactly the same manner as other precise surveying instruments.

The alloy metal is relatively soft and can easily break or kink if mishandled. Ordinarily, you should not use Invar tapes when a steel tape can give the desired accuracy under the same operating conditions. Use Invar tapes only for very precise measurements, such as those for base lines and in city work. When not in use, the tape should be stored in a reel. Except for special locations where the ground surface is hard and flat, such as roadways or railroads beds, use the Invar tape over special supports or stools and do not permit it to touch the ground.

5.3.0 Surveying Accessories

Surveying accessories include the equipment, tools, and other devices that are not an integral part of the surveying instrument itself. They come as separate items; thus, they are ordered separately through the Navy supply system.

When you run a traverse, for example, your primary instruments may be the transit and the steel tape. The accessories you need to do the actual measurement will be the following: a tripod to support the transit, a range pole to sight, a plumb bob to center the instrument on the point, perhaps tape supports if the survey is of high precision, and so forth You must become familiar with the proper care of this equipment and use it properly.

5.3.1 Tripod

The tripod is the base or foundation that supports the survey instrument and keeps it stable during observations. A tripod consists of a head to which the instrument is attached, three wooden or metal legs that are hinged at the head, and pointed metal shoes on each leg to be pressed or anchored into the ground to achieve a firm setup. The leg hinge is adjusted so that the leg will just begin to fall slowly when it is raised to an angle of about 45°. The tripod head may have screw threads on which the instrument is mounted directly, a screw projecting upward through the plate, or a hole or slot through which a special bolt is inserted to attach to the instrument. Two types of tripods are furnished to surveyors: the fixed-leg tripod and the extension leg tripod. The fixed-leg type is also called a stilt-leg or rigid tripod, and the extension leg tripod is also called a jack-leg tripod (Figure 12-15). Each fixed leg may consist of two lengths of wood as a unit or a single length of wood split at the top and attached to a hinged tripod head fitting and to a metal shoe.

 

Figure 12-15 – Types of tripods.

At points along the length of the tripod legs, perpendicular brace pieces are sometimes added to give greater stability. The extension tripod leg is made of two sections that slide longitudinally. On rough ground, the legs are adjusted to different lengths to establish a horizontal tripod head or to set the instrument at the most comfortable working height for the observer.

You must swing the fixed legs in or out in varying amounts to level the head. Instrument height is not easy to control, and the you must learn the correct spread of the legs to get the desired height. Wide-frame tripods have greater torsional stability and tend to vibrate less in the wind.

Grip the surveying instrument firmly to avoid dropping it while you are mounting it on the tripod. Hold the transit by the right standard (opposite the vertical circle) while you are attaching it. Hold the engineer’s level at the center of the telescope, but grip theodolites and precise levels near the base of the instrument. Screw the instruments down to a firm bearing but not so tightly that they will bind or the screw threads will strip.

In setting up the tripod, place the legs so that setup is stable. On level terrain, you can achieve this by having each leg form an angle of about 600 with the ground surface. Loosen the restraining strap from around the three legs, and secure it around one leg. An effective way to set the tripod down is to grip it with two of the legs close to the body while you stand over the point where the setup is required.

With one hand, push the third leg out away from the body until it is about 50° to 60° with a horizontal. Lower the tripod until the third leg is on the ground. Place one hand on each of the first two legs, and spread them while taking a short backward step, using the third leg as a pivot point. When the two legs look about as far away from the mark as the third one and all three are about equally spaced, lower the two legs and press them into the ground. Make any slight adjustment to level the head further by moving the third leg a few inches in or out before pressing it into the ground.

On smooth or slippery paved rock surfaces, tighten the tripod legs hinges while setting up to prevent the legs from spreading and causing the tripod to fall. Make use of holes or cracks in the ground to brace the tripod. In some cases, as a safety factor, tie the three legs together or brace them with rock or bushes after they are set to keep them from spreading. If you are setting up on a slippery finished floor, you may fit rubber shoes to the metal shoes, or use an equilateral triangle leg retainer to prevent the legs from sliding.

When setting up on steeply sloping ground, place the third leg uphill and at a greater distance from the mark. Set the other two legs as before, but before releasing them, check the stability of the setup to see that the weight of the instrument and tripod head will not overbalance and cause the tripod to slip or fall.

Take proper care in handling the tripod. When the legs are set in the ground, be careful to apply pressure longitudinally. Pressure across the leg can crack the wooden pieces. Adjust the hinge joint and do not over tighten it enough to cause strain on the joint or strip or lock the metal threads. Keep the machined tripod head covered with the head cover or protective cap when you are not in using it, and do not scratch or burr the head by mishandling it. When using the tripod, place the protective cap in the instrument box to prevent it from being misplaced or damaged. Any damage to the protective cap can be transferred to the tripod head. Remove any mud, clay, or sand adhering to the tripod, and wipe the tripod with a damp cloth and dry it. Coat the metal parts with a light film of oil or wipe them with an oily cloth. Foreign matter can get into hinged joints or on the machined surfaces and cause wear. Stability is the tripod’s greatest asset. Instability, wear, or damaged bearing surfaces on the tripod can evolve into unexplainable errors in the final survey results.

5.3.2 Range Pole

A range pole (also called a lining rod) is a wood or metal pole, usually about eight feet long and about 1/2 to one inch in diameter; it is has a steel point or shoe and painted bands of alternating red and white to increase its visibility. The range pole is held vertically on a point or plumbed over a point, so the point may be observed through an optical instrument. Its primary use is as a sighting rod for linear or angular measurements. For work of ordinary precision, chainmen may keep on line by observing a range pole. A range pole may also be used for approximate stadia measurement.

5.3.3 Plumb Bob, Cord, and Target

A plumb bob is a pointed, tapered brass or bronze weight that is suspended from a cord for the general purpose of determining the plumb line from a point on the ground. Common weights for plumb bobs are 6, 8, 10, 12, 14, 16, 18, and 24 oz; the 12- and the 16- oz are the most popular.

A plumb bob is a precision instrument and you must care for it as such. If the tip becomes bent, the cord from which the bob is suspended will not occupy the true plumb line over the point indicated by the tip. A plumb bob usually has a detachable tip, so if the tip becomes damaged, you can renew it without replacing the entire instrument.

Each survey party member should be equipped with a leather sheath, and the bob should be placed in the sheath whenever it is not in use. To make the cord from a plumb bob more conspicuous for observation purposes, attach an oval form aluminum target (Figure 12-16A).

 

Figure 12-16 – The plumb bob, cord, and target.

The oval target has reinforced edges, and the face is enameled in quadrants alternately with red and white. Also, you may use a flat rectangular plastic target (Figure 12-16B). It has rounded corners with alternate red and white quadrants on its face. These plumb bob string targets are pocket size with approximate dimensions of 2 by 4 inches.

5.3.4 Optical Plumbing Assembly

The optical plumbing assembly, or plummet, is a device built into the alidade or the tribrach of some instruments to center the instrument over a point. The plummet consists of a small prismatic telescope with a cross wire or marked circle reticle adjusted to be in line with the vertical axis of the instrument. After the instrument is leveled, a sighting through the plummet will check the centering over a point quickly. The advantages of the plummet over the plumb bob are that it permits the observer to center over a point from the height of the instrument stand, and it is not affected by the wind. The plummet is especially useful for work on high stands. A plumb bob requires someone at ground level to steady it and to inform the observer on the platform how to move the instrument and when it is exactly over the point. With the plummet, the observer does the centering and checking.

5.3.5 Tape Accessories

There is usually a leather thong at each end of a tape by which you can hold the tape when using the full length. When using only part of the tape, you can hold the zero end by the thong, and hold the tape at an intermediate point by means of a tape clamp handle. When a tape is not supported throughout— that is, when it is held above ground between a couple of crew members—you must apply a correction for the amount of sag in the tape. To make this correction, apply a certain amount of tension using a tension scale and/or spring balance (Figure 12-17).

 

Figure 12-17 – The tension scale and spring balance.

The tension scale is graduated in pounds from 0 to 30. It is clipped to the eye at the end of the tape, and the tension is applied until the desired reading appears on the scale. A pair of staffs can be used to make the work easier. Wrap the rawhide thongs around the staff at a convenient height and grip them firmly. Brace the bottom end of the staff against the foot and tuck the upper end under the arm. Apply tension by using the shoulder and leaning against the poles. Use the spring balance in a similar fashion for work of higher precision.

The stool device is called a tapping stool or chaining buck and is used in high precision work. It is a metal three-legged stand with an adjustable sliding head and a hand wheel operating device for locking the plate (the top surface of the sliding head) in any desired position. A line is scribed on the plate. During taping operations, move the head until the scribed line is directly under a particular graduation on the tape; then use the hand wheel to lock the head. When the tape is shifted ahead to measure the next interval, hold the graduation exactly over the line until the next stool is adjusted and locked. The basic purpose of taping stools is to furnish stable, elevated surfaces on which taped distances can be marked accurately. When stools are not available, 2 by 4s or 4 by 4s are often driven into the ground for use as chaining bucks.

The length of a tape varies with the temperature, and the precision of a survey may require you to apply corrections for this. For work of ordinary precision, you can assume that the temperature of the tape is about the same as that of the air. For work requiring higher precision, attach a tape thermometer to the tape. For very precise work, use two thermometers, one positioned at each end. If the two indicate different temperatures, use the mean between them.

5.3.6 Chaining Pin

A chaining pin (also called a taping arrow) is a metal pin about one foot long. It has a circular eye at one end and a point for pushing it into the ground at the other. These pins come in sets of 11 pins, carried on a wire ring passed through the eyes in the pins or in a sheath called a quiver.

Chaining pins can be used for the temporary marking of points in a great variety of situations, but they are used most frequently to keep count of tape increments in the chaining of long distances.

5.3.7 Leveling Rod, Target, and Rod Level

A leveling rod, is a tape supported vertically and is used to measure the vertical distance (difference in elevation) between a line of sight and a required point above or below it. This point may be a permanent elevation (bench mark), or it may be some natural or constructed surface.

There are several types of leveling rods. The most popular of all, the Philadelphia rod, (Figure 12-18), is a graduated wooden rod made of two sections and extendable from 7 to 13 feet.

 

Figure 12-18 – The Philadelphia rod.

Each foot is subdivided into hundredths of a foot. Instead of each hundredth being marked with a line or tick, the distance between alternate ones is painted black on a white background. Thus, the value for each hundredth is the distance between the colors; the top of the black, even values, the bottom of the black, odd values. The tenths are numbered in black, the feet in red. This rod may be used with the level, transit, theodolite, and with the hand level on occasion to measure the difference in elevation.

The instrumentman reads the leveling rod directly by the sighting through the telescope, or it may be target-read. Conditions that hinder direct reading, such as poor visibility, long sights, and sights partially obstructed by, for example, brush or leaves, sometimes necessitate using targets. The target is also used to mark a rod reading when numerous points are set to the same elevation from one instrument setup. Targets for the Philadelphia rod are usually oval, with the long axis at right angles to the rod, and the quadrants of the target painted alternately red and white. The target is held in place on the rod by a C-clamp and a thumbscrew. A lever on the face of the target is used for fine adjustment of the target to the line of sight of the level. The targets have rectangular openings approximately the width of the rod and 0.15 feet high through which you can see the face of the rod. A linear vernier scale is mounted on the edge of the opening with the zero on the horizontal line of the target for reading to thousandths of a foot. When the target is used, the rodman takes the rod reading.

The other types of leveling rods differ from the Philadelphia rod only in details. The Frisco rod, for direct reading only, is available with two or three sliding sections. The Chicago rod is available with three or four sections that, instead of sliding, are joined at the end to each other like a fishing rod. The architect’s or builder’s rod is a two-section rod similar to the Philadelphia but graduated in feet and inches to the nearest one-eighth inch rather than decimally. The upper section of the Lenker self-computing rod has the graduations on a continuous metal belt that can be rotated to set any desired graduation at the level of the height of the instrument (HI). To use the rod, set the rod on the bench mark and bring the graduation that indicates the elevation of the bench mark level with the HI. As long as the level remains at that same setup, wherever you set the rod on a point, you read the elevation of the point directly. In short, the Lenker rod does away with the necessity for computing the elevations. The targets furnished with the metric rod have a vernier that permits reading the scale to the nearest millimeter. The metric rod can be extended from 2.0 to 3.7 meters.

For high-precision leveling, there are precise leveling rods as well as precise engineer’s levels. A Lovar rod is usually T-shaped in cross section and has the scale inscribed on a strip of Lovar metal. A precise rod usually has a tapering, hardened steel base. Some are equipped with thermometers for applying temperature correction. Precise rods generally contain built-in rod levels.

A rod reading is accurate only if the rod is perfectly plumbed. If it is out of plumb, the reading will be greater than the actual vertical distance between the HI and the base of the rod. Therefore, to ensure a truly plumbed leveling rod, use a rod level. There are two types of rod levels generally used with standard leveling rods (Figure 12-19). The one at the left is called the bull’s-eye level, and one on the right is the vial level.

 

Figure 12-19 – Types of rod levels.

Take proper care of leveling rods. The care consists of keeping them clean, free of sand and dirt, unwarped, and readable. Always carry them over the shoulder or under the arm from point to point. Dragging them through the brush or along the ground will wear away or chip the paint. When they are not in use, store the leveling rods in their cases to prevent warping. The cases are generally designed to support the rods either flat or on their sides. Do not lean them against a wall or allow them to remain on damp ground for any extended period, since this can produce a curvature in the rods and result in unpredictable random and systematic errors in leveling.

5.3.8 Stadia Boards

To determine linear distance by stadia, observe a stadia rod or stadia board through a telescope containing stadia hairs, and note the size of the interval intercepted by the hairs. Each tenth of a foot is marked by the point of one of the black, saw-toothed graduations. The interval between the point of a black tooth and the next adjacent white gullet between two black teeth represents 0.05 feet.

5.3.9 Turning-Point Pins and Plates

The point on which a leveling rod is held between a foresight and the next back sight while the instrument is being moved to the next setup is called a turning point. It must be sufficiently stable to maintain the accuracy of the level line. Where neither proper natural features nor man-made construction is available, use a turning-point pin, a turning-point plate, or a wooden stake. These not only furnish the solid footings but also identify the same position for both sightings. Normally, you use the pins or plates for short periods and take them up for future use as soon as you complete the instrument readings. Use wooden stakes for longer periods except when wood is scarce or local regulations require their removal. A turning-point pin (Figure 12-20) is made of a tapered steel spike with a round top with a chain or a ring through the shaft for ease in pulling. Drive the pin into the ground with a sledgehammer. After a turning pin has served its purpose at one point, pull it and carry it to the next turning point.

 

Figure 12-20– The turning-point pin and plate.

Turning-point plates (Figure 12-20) are triangular metal plates with turned-down corners or added spikes that form prongs and have a projection or bump in the center to accept the rod. The plates are used in loose, sandy, or unstable soils. Set the plate by placing it on the ground, points down, and stepping on it to press it to a firm bearing. After using it, lift it; shake it free of dirt and mud, and carry it forward to the next turning point.

5.3.10 Magnifying Glass

A magnifying glass is used mainly to aid the instrumentman in reading graduations that are provided with verniers, such as the horizontal and vertical circle of a transit. Although these graduations can be read with the naked eye, a magnifying glass makes the reading easier and decreases the chance of reading the wrong coincidence.

The transit box typically comes equipped with a 3x and 10x pocket magnifying glass. To avoid unknowingly dropping a magnifying glass in the field, attach it to a loop of string. The instrumentman puts his or her head through the loop, retaining the string around the neck, and carrying the magnifying glass in a pocket. At the end of each day’s work, always return the magnifying glass to its proper place in the instrument case.

5.3.11 Adjusting Pins

Surveying instruments are built to allow minor adjustments in the field without much loss of time while the work is in progress. The adjustments are made by loosening or tightening the capstan screws turned with adjusting pins. These pins are also included   12-36 in the instrument box. They come in various sizes depending upon the type of instrument and the hole sizes of its capstan screws. Use the pin that fits the hole in the capstan head. A pin that is too small, will ruin the head of the screw.

Surveying instrument dealers usually replace these pins free of charge. Like the magnifying glass, adjusting pins should be carried in the pocket and not left in the instrument box while a survey is in progress. This will save a lot of valuable time when you need the pins. Do not use wires, nails, screwdrivers, and the like, as substitutes for adjusting pins.

5.3.12 Tape Repair Kit

Even though you handle the tape properly and carefully during field measurements, some tapes still break under unforeseen circumstances. During chaining operations, when the area is quite far from the base of operations, always be sure to have a tape repair kit with you so that you can rejoin any broken tape in the field, or if you has bring an extra tape, you can take the broken tape back to the office for repair.

The tape repair kit usually contains a pair of small snips, the tape sections of proper size and graduations, a hand punch or bench punch with block, an assortment of small rivets, a pair of tweezers, a small hammer, and a small file. Before reusing a repaired tape, always compare it with an Invar or Lovar tape to check it for accuracy.

Test Your Knowledge

10. Which of the following tools is best suited for driving pipe markers into surfaces?

A. A hatchet
B. A single bit ax
C. A sledgehammer
D. A bull point

11. After you secure the restraining strap, what is the next step in setting up a tripod?

A. Hold one leg close to your body
B. Hold two legs close to your body
C. Spread the legs, 60 degrees apart
D. Spread the legs until they form about a 50-60 degree angle with the horizontal

12. Which of the following tape accessories should be used to hold the tape securely at an intermediate point?

A. Tape clamp handle
B. Tensions scale
C. Taping stool
D. Staff

 

6.0.0 FIELD SUPPLIES

Field supplies are a variety of materials used to mark the locations of points in the field. For example, pencils, field notebooks, and spare handles for sledgehammers are generally classified as field supplies. Every operation site may require different supplies, but your own experience and the aid of your leading petty officer will allow for making a comprehensive list of supplies necessary for a projected survey mission. This section describes the items generally required for a mission.

6.1.0 Survey Point Markers

The material used as a survey point marker depends upon where the point is located and whether the marker is to be temporary, semi permanent, or permanent. For example, a wooden stake can be easily driven to mark the location of a point in a grassy field, but it cannot be used to mark a point on the surface of a concrete highway.

Similarly, though a wooden stake is easy to drive in a grassy field to mark a property line corner, a marker of this kind would not last as long as a piece of pipe or a concrete monument. The following sections describe most of the material commonly used as semi permanent or permanent markers of points in the field. For purely temporary marking, it is often unnecessary to expend any marking materials. For example, a point in ordinary soil is often temporarily marked by a hole made with the point of a plumb bob, a chaining pin, or some other pointed device. In rough chaining of distances, even the mere imprint of a heel in the ground may suffice. A point on a concrete surface may be temporarily marked by an X drawn with keel (lumber crayon), a pencil, or some similar marking device. A large nail serves well as a temporary point in relatively stable ground or compacted materials.

6.1.1 Semi Permanent Markers

Wooden hubs and stakes are extensively used as semi permanent markers of points in the field. The principal distinction between the two is the fact that a hub is usually driven to bring its top flush with, or almost flush with, the ground surface. A hub is used principally to mark the station point for an instrument setup. It is usually made of two by two inch stock and is from five to twelve inches long. The average length is about eight inches. Shorter lengths are used in hard ground, longer lengths in softer ground. A surveyor’s tack, made of galvanized iron or stainless steel with a depression in the center of the head, is driven into the top of the hub to locate the exact point where the instrument is to be plumbed.

Stakes improvised in the field may be cylindrical or any other shape available. However, manufactured stakes are rectangular in cross section because the faces of a stake are often inscribed with data relevant to the point the stake is marking. A stake that marks a bench mark, for instance, is inscribed with the symbol that identifies the bench mark and with the elevation. A stake that marks a station on a traverse is inscribed with the symbol of the particular station, such as 2 + 45.06. A grade stake is inscribed with the number of vertical feet of cut (material to be excavated) or of fill (material to be filled in) required to bring the elevation of the surface to the specified grade elevation.

6.1.2 Permanent Markers

Permanent station markers are used to mark points to be used for a long period of time. Horizontal and vertical control stations are generally marked with permanent markers. These markers could be in the following forms:

All permanent survey station markers should be referenced so they can be replaced if disturbed. Methods of referencing points are discussed later in this training manual.

Surveyor’s tacks, spikes, and nails are often driven into growing trees, bituminous, or other semisolid surfaces as permanent markers. A nail will be more conspicuous if it is driven through a bottle cap, washer, plastic tape, or “shiner”. A shiner is a thin metal disk much like the top or bottom of a frozen fruit juice can. A spad is a nail equipped with a hook for suspending a plumb bob. It is driven into an overhead surface, such as the top of a tunnel. The plumb bob will locate on the floor the point vertically below the point where the spad is driven. Points on concrete or stone surfaces are often marked with an X cut with a hammer and chisel. Another way to do this is to cut holes with a star drill and then plug them with lead.

A much more durable form of marker is made of a length of metal pipe—usually called iron pipe regardless of the actual metal used. Lengths run from about 18 to 24 inches. Sawed-off lengths of pipe have open ends; pipes cut with a shear have pinched ends and are called pinch pipe. There are also manufactured pipe markers, some of which are T-shaped rather than cylindrical in cross section. A commercial marker may be a copper-plated steel rod. All commercial markers have caps or heads that permit center punching for precise point location and stamping of the identifying information.

A still more durable form of marker is the concrete monument. A short length of brass rod is often set in the concrete to mark the exact location of the point. Concrete monuments used as permanent markers by various federal survey agencies have identifying disks set in concrete (Figure 12- 21).

 

Figure 12-21 -Various types of federal marking disks.

Points on concrete or masonry surfaces may be permanently marked by setting lengths of cylindrical brass stock into holes plugged with lead or grout. Brass stock markers set in pavement are commonly called coppers. Manufactured brass disks may be set in grouted holes in street pavements, sidewalks, steps, or the tops of retaining walls. Points on bituminous surfaces maybe marked by driving in pipe, railroad spikes, or case-hardened masonry nails, commonly called PK nails. A center punch for marking a precise location on metal stock or metal caps is a common item of equipment for a surveyor.

6.2.0 Marking Materials

Keel, or lumber crayon, is a thick crayon used for marking stakes or other surfaces. Common marking devices containing quick-drying fluid and a felt tip are also popular for marking stakes. All of these types of graphic marking materials come in various colors. In addition to keel, paint is used to mark pavement surfaces. Paint may be brushed on or sprayed from a spray can. To make the location of a point conspicuous, use a circle, cross, or triangle. Identification symbols, such as station or traverse numbers, may also be painted on. For a neater job, stencils are sometimes used.

6.3.0 Flagging

Colored cloth bunting or plastic tape is often used to make stakes conspicuous so they will be easier to find or to warn Equipment Operators away. Flagging may also be used for identification purposes. For example, traverse stakes may be marked with one color, grade stakes with another. Red, yellow, orange, and white are the most popular colors for flagging.

6.4.0 Note-Keeping Materials

Field notes are usually kept in a bound, standard field notebook. Sometimes loose-leaf notebooks are used but are not generally recommended because of the chance of losing pages. Notebooks are classified as engineer’s or transit field books, level books, cross section books, and so forth, depending on their use.

In a transit book, the left-hand side of the page is used for recording measurement data, and the right-hand side of the page, for remarks, sketches, and other supplementary information. The other field books generally follow the same pattern of usage. A transit or a level book may be used for recording any type of survey. You may add or modify the column headings to suit the required data you desire to record.

6.5.0 Personal Protective and Safety Equipment

In addition to the necessary field supplies and equipment, a field party must carry all necessary items of personal protective equipment, such as containers for drinking water, first-aid kits, gloves, and foul weather gear. A field survey party is usually working a considerable distance away from the main operational base. If, for example, you happen to be chaining through a marsh filled with icy water, you would not have a chance to return to the base to get your rubber boots.

You are required to wear a hard hat whenever you work in a construction area where the assigned personnel are regularly required to wear hard hats. Study all situations in advance, considering both the physical and environmental conditions—doing so may avoid situations dangerous to you and other crewmembers.

 

Test Your Knowledge

15. The type of material to be used for survey point markers depends upon which of the following conditions?

A. The location of the point
B. Whether the point is temporary or permanent
C. The discretion of the engineer officer
D. Both A and B

16. Which of the following types of markers is/are generally used for horizontal and vertical control stations?

A. Iron pipe filled with concrete
B. Bronze disks set in concrete
C. A hole drilled in concrete and filled with lead
D. All of the above

 

Summary

In this lesson, you were presented with information relevant to safe, efficient, and effective methods and applications. Specifically, you learned about survey classification, types of survey operations, standard issue surveying instruments, field equipment, and field supplies. Through clear comprehension of surveying theory and procedures, not only will your work as a surveyor be sought out within the industry, but the quality and precision of your efforts will be second to none.

Review Questions

 1. In surveying, the vertical position of a point is determined in which of the following ways?

A. Measuring directly from a datum
B. Measuring indirectly from a datum
C. Computation from differences in elevation that are measured directly or indirectly from a datum

2. Increasing the areas surveyed with plane surveying methods will have what effect on (a) accuracy and (b) precision?

A. (a) Increase (b) decrease
B. (a) Decrease (b) decrease
C. (a) Decrease (b) increase
D. (a) Increase (b) increase

3. Determining the directions and elevations of a new highway requires what kind of survey?

A. Topographic
B. Construction
C. Route
D. Land

4. Which of the following types of surveys is also known as an engineering survey?

A. Route
B. Construction
C. Topographic
D. Cadastral

5. In surveying practice, which, if any, of the following tasks is considered to be an element of office work?

A. Computing and plotting necessary information
B. Taking measurements
C. Collecting engineering data
D. None of the above

6. In general, which, if any, of the following actions will best predetermine field conditions and allow the selection of methods to be used for a survey?

A. Reviewing topographic maps
B. Site reconnaissance
C. Checking local weather conditions
D. None of the above

7. Which of the following conditions must be considered when determining the size of a field survey party?

A. The availability of equipment
B. The methods that will be used
C. The requirements of the survey
D. All of the above

8. A transit party should consist of at least what three people?

A. Instrumentman, rodman, and note keeper
B. Rodman, head chainman, and note keeper
C. Party chief, head chainman, and instrumentman
D. Instrumentman, head chainman, and note keeper

9. In field notebooks, all lettering should be performed in a freehand Gothic style with which of the following grades of pencil lead?

A. 2H or 3H
B. 3H or 4H
C. 4H or 5H

10. Where in the field notebook should name and location of the project, the types of measurements, and the designation of the survey unit be written?

A. Front cover
B. Inside front cover
C. Right-hand pages

11. Instructions for returning the notebook if it is lost belong in what part of the field notebook?

A. On the front cover
B. Inside the front cover
C. On the right-hand pages

12. In keeping field notes, which of the following procedures is/are mandatory?

A. Notes are never kept on individual scraps of paper for later transcription to notebooks.
B. Erasures are never permitted; incorrect entries are lined-out and correct entries inserted.
C. Rejected pages are neatly crossed-out and referenced to the substituted pages.
D. All of the above

13. In a measured distance that required 200 measurements, the total error was -9 units. For this error to be adjusted, each measurement must be:

A. Increased by 0.045
B. Increased by 0.450
C. Decreased by 0.450
D. Decreased by 0.045

14. A measured distance is 302.12 feet. This measurement contains what total number of significant figures?

A. Five
B. Two
C. Three
D. Four

15. If you round off 92.454 to three significant figures, what is the resulting number?

A. 92.4
B. 92.5
C. 92.40
D. 92.50

16. When drawing a property map, you should include which of the following items?

A. The length and direction of each boundary line
B. Reference points referred from an established coordinate system
C. Names of important details, such as roads, streams, and landmarks.
D. All of the above

17. In an orientation symbol, a full-head arrow represents what direction or orientation information, if any?

A. Magnetic meridian
B. True meridian
C. Magnetic declination
D. None

18. Which of the following factors will influence the orientation of a map drawn on standard size drawing paper?

A. The shape of the mapped area
B. The size of the mapped area
C. The scale of the map
D. The purpose of the map

19. A map that should be used for making a model of an 18-hole golf course is known as what type?

A. Geographic
B. Planimetric
C. Topographic

20. An ordinary road map of the state of Florida is an example of what type of map?

A. Geographic
B. Planimetric
C. Topographic

21. A naval station base map that shows only the layout of buildings and roads is what type of map?

A. Geographic
B. Planimetric
C. Topographic

22. For a one minute theodolite, which of the following actions occur when the circle clamp is in the lever-down position?

A. The circle is clamped and turns with the telescope.
B. The circle is clamped and the telescope turns independently.
C. The circle is unclamped and the telescope turns independently.
D. The circle is unclamped and turns with the telescope.

23. The lower half of the vertical line on the reticle of a theodolite is split for what purpose?

A. To center triangular-shaped distant objects
B. To determine the width of distant objects
C. To center small distant objects
D. To determine the height of distant objects

24. What are the values read from the vertical circle of a theodolite called?

A. Vertical angles
B. Direct angles
C. Zenith distances
D. Direct distances

25. What part of a one second theodolite is used to select whether the angle being read is a vertical or horizontal angle?

A. Circle tangent screw
B. Inverter knob (circle-selector)
C. Circle setting knob
D. Circular level

26. The difference between two diametrically opposite members on the circle of a one second theodolite as viewed through the circle reading microscope is equal to plus or minus how many degrees?

A. 90
B. 180
C. 270
D. 360

27. The bubble of a level vial on the surveying instrument may become increasingly difficult to center because of what factor?

A. Temperature
B. Vial age
C. Humidity
D. Vial sensitivity

28. On a tilting level, which of the following screws is used to bring the bubble to the exact center?

A. Tangent
B. Micrometer
C. Leveling
D. Centering

29. The purpose of the compensator in a self-leveling level is to compensate for which of the following factors?

A. Misalignment of the vertical hair only
B. Misalignment of the horizontal hair only
C. Misalignment of both the vertical and horizontal hairs
D. A slight out-of-level of the telescope

30. Which of the following tools should you use when cleaning away small saplings and vines?

A. Chain saw
B. Brush hook
C. Coping saw
D. Bull point

31. Which of the following tools should you use to lift a manhole cover?

A. A long-handled shovel
B. A crowbar
C. A long-bladed screwdriver
D. A machete

32. Which, if any, of the following devices is used to locate buried metal markers?

A. Dip needle
B. Mine detector
C. Probing steel
D. None of the above

33. Which of the following tapes should be used for the high-precision measurement of a base line that is in the vicinity of a high-voltage circuit?

A. Metallic
B. Nonmetallic
C. Steel
D. Invar

34. To run a traverse in steep terrain on a windy day, which of the following tripods should you use to support the transit?

A. Stilt-leg
B. Wide-frame rigid
C. Wide-frame jack-leg
D. Jack-leg

35. The effectiveness of the plumb bob, cord, and target set as a precision instrument will be post impaired by what condition?

A. Faded paint on the target
B. Dust on any part of the set
C. A damaged or bent tip on the plumb bob
D. A worn leather sheath

36. In high-precision measurement, which of the following tape accessories should be used to mark accurately the distance indicated by the tape graduation?

A. Tension scale
B. Taping stool
C. Staff
D. Tape thermometer

37. When target reading is being performed, what survey party member reads the rod?

A. Chainman
B. Instrumentman
C. Flagman
D. Rodman

38. During leveling operations, in which of the following soil conditions should you use a turning point plate?

A. Sandy or muddy soil
B. Compacted gravel
C. Ordinary stable soils
D. Rocky pasture land