The accuracy and quality of any survey will depend upon the skills and abilities of the survey crew. However, the underlying foundation for a crew’s accurate survey is the quality and condition of the surveying equipment. Equipment that has not been cared for and maintained becomes inaccurate, and inaccurate equipment will negatively affect a survey regardless of the skills of the crew. Taking proper care of your survey equipment cannot be overemphasized; therefore, the first part of this lesson will address proper instrument handling, stowing, and maintenance practices. The second part of this lesson will address instrument adjustment and repair. As used in this lesson, the term “adjustment” means bringing the various fixed parts of an instrument into proper relationship with one another. It is different from the ordinary operations of leveling the instrument, aligning the telescope, and so forth. As an engineering tech, you need to be able to correctly maintain the equipment and adjust the fixed elements into sync as a matter of routine.
When you have completed this lesson, you will be able to:
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1.0.0 Care of Instruments
2.0.0 Instrument Adjustments and Repairs |
A user’s manual accompanies every survey instrument in the Table of Allowance (TOA). Each manual provides information on the appropriate care and maintenance of a specific instrument as well as instructions on the functions, operations, and adjustments of its various components. You should thoroughly study each user’s manual, such as the one shown in Figure 17-1, before you attempt to use that instrument. Some suggestions for the care and maintenance of surveying equipment are discussed in the following paragraphs.
1.1.0 Handling, Carrying, and Stowing When you handle any surveying instrument, such as the transit, level, theodolite, or plane table, always exercise great care. Each is a precision instrument intended for operation in the robust world of construction. CAUTION NEVER leave an instrument unattended while set up on a street, near construction work, or in any other place where it can be damaged. CAUTION NEVER grasp the telescope to remove an instrument from its carrying case. Wrenching the telescope could damage a number of delicate parts. When you set up an instrument, make sure it is securely fastened to the tripod head. However, only tighten the various clamp screws, leveling screws, and adjustment screws to a firm bearing; overtightening could strip the threads, twist off the screw, bend the connecting part, or place undue stresses on the instrument. When you carry an instrument, ensure that all clamp screws are only lightly clamped so that the parts will move if the instrument is struck. When you carry a tripod-mounted instrument, place it on one shoulder with the tripod legs pointing forward, and hold them together with your hand and forearm. If you are walking on the side of a hill, carry the instrument on the downhill shoulder; this leaves the uphill arm and hand free to catch yourself if you trip or stumble. Do not carry an instrument on your shoulder through doorways or beneath low-hanging branches; under those circumstances, carry it under your arm with the head of the instrument to the front. Figure 17-1 — Typical theodolite user’s manual. NAVEDTRA 10469A 17-4 If you need to climb over a fence, first place the instrument on the other side with the tripod legs well spread. Every transit, theodolite, or level comes equipped with a carrying box or case so the instrument and its accessories can be stowed in a manner that ensures a minimum of motion during transportation. Always stow an instrument in its carrying case when not in use. (Figure 17-2) For carrying stakes and hubs, canvas bags with shoulder straps are usually provided. They closely resemble a newsboy’s bag. In fact, a newsboy’s bag makes an excellent carrying bag for stakes and hubs, as does a Navy seabag equipped with a shoulder strap. (Figure 17-3) Also provided are various other types of leather or canvas bags and sheaths for items such as chaining-pin quivers, plumb-bobs, and Abney and Locke levels. Most of these can be attached to the belt. In addition, leather pouches, also usually attachable to the belt, are available for carrying small hand tools, marking equipment, turning-point pins, and the like. In time, you will learn various conveniences, such as carrying your supply of surveyor’s tacks by sticking them in a rubber ball or a piece of softwood attached to your belt.
1.2.0 Cleaning and Lubrication You must clean all surveying instruments, equipment, or tools immediately after you use them. Dust off the transit or theodolite and wipe it dry before you place it back in its case. Remove all dust with a soft brush before wiping dirty components with a clean Figure 17-2 — Examples of typical instrument cases. Figure 17-3 — Typical bags for stakes and hubs. NAVEDTRA 10469A 17-5 cloth. If the instrument becomes wet, remove it from its carrying case and dry it thoroughly at room temperature once you get back to your workstation. CAUTION NEVER leave a wet instrument stored in the carrying case. CAUTION NEVER rub the lenses of a telescope with your fingers or a rough cloth. Use a lint-free soft cloth or clean chamois leather instead. Occasionally, you may need to clean the lenses with a soft cloth dampened with a mixture of equal parts water and alcohol. Immediately after each use, always remove mud and dirt from tripods, range poles, leveling rods, and so forth, especially when the surveying gear is made of a material susceptible to rust or decay. When lubricating instruments, always use the right lubricant recommended for the climatic condition in your area. For instance, in sub-zero temperatures, graphite is the recommended lubricant for a transit’s moving parts, while a light film of oil (preferably watch oil) is the recommendation in warmer climates. If you are ever in doubt, before doing anything to an instrument, consult the manufacturer’s manual or your senior engineering tech.
Properly maintaining equipment to inspection standards facilitates quality work and accurate surveys. As part of their tasking, Engineering techs make minor adjustments and repairs to surveying instruments, that is, those that can generally be done in the field using simple tools. Major adjustments and major repairs generally need to be done in the factory. If the instrument’s defect cannot be corrected by a minor adjustment or minor repair, do not attempt to disassemble it; instead, arrange to send the instrument to the manufacturer. Most surveying instruments are precision instruments that require special skills and tools for major adjustments and recalibration. Only the instrument company or its subsidiaries can provide these.
2.1.0 Instrument Adjustments As stated previously, in this lesson, adjustment means the process of bringing the various parts of an instrument into proper relationship with one another. To be a qualified surveyor, you must have the ability to make these adjustments. To make proper adjustments, a qualified surveyor must: 1. Be familiar with the principles upon which the adjustments are based. 2. Know the methods or tests used to determine if an instrument is out of adjustment. 3. Know the procedure and sequence for making adjustments. 4. Be able to tell what effect an adjustment of one element will have on other parts. 5. Understand the effect of each adjustment when it is actually used for measurement. NAVEDTRA 10469A 17-6 Generally, instrument adjustments involve the level tubes, the telescope, and the reticle [ret-i-kuhl]; for example, if one or both of the plate-level bubbles of an engineer’s transit are centered when the plate is, in fact, not level, the instrument is out of adjustment. An optical instrument equipped with vertical and horizontal cross hairs is out of adjustment if the point of intersection between the cross hairs does not coincide with the optical axis. If the reflected bubble on a Locke or Abney level is centered when the optical axis is other than horizontal, the instrument is out of adjustment. Adjustment chiefly involves a step or a sequence of steps necessary to bring a bubble to center when it should be at center, or bring a crosshair point of intersection into coincidence with the optical axis. Instrument manufacturers publish handbooks detailing recommended adjustment procedures, usually as small pamphlets, obtainable free of charge. The following topics are intended to give you a general overview of instrument adjustment procedures. However, for adjusting a particular instrument, you need to follow the appropriate manufacturer’s instructions. 2.1.1 General Adjustment Procedures Carefully check your instruments periodically to determine whether they need adjustment. A modern adage advises, “An instrument should be checked frequently but adjusted rarely.” The basis for this saying lies in the fact that modern quality instruments get out of adjustment much less frequently than generally believed. The need for an adjustment is often caused by a previous adjustment that was unnecessary but occurred because of errors in checking. Before assuming that adjustment is necessary, you must positively ascertain that maladjustment actually exists. In general, apply the following procedures to all tripod-mounted optical instruments: (Figure 17-4) 1. Check the instrument on a cloudy day, if possible. 2. Ensure that the tripod shoes are tight and that the instrument is screwed all the way down on the tripod. 3. Set the tripod up on firm ground in the shade but in a good light where you can sight at least 200 feet in opposite directions. 4. Spread the tripod feet well apart and place them so that the plate is approximately level. Press the shoes in firmly, or set them in cracks or chipped depressions if on a hardened surface. (Avoid setting up on asphalt pavement in warm weather.) 5. After the tripod feet are set, loosen and retighten the wing nuts to release any possible residual friction that, if not released, might cause an eventual shift in the legs. Figure 17-4 — Typical surveyor’s tripod. NAVEDTRA 10469A 17-7 6. Level the instrument with particular care, then loosen all level screws slightly (again to release residual friction) and relevel. Tighten all screws with equal firmness but do not over tighten. Too much tightness will eventually deform the centers, causing both friction and play. 7. Carry out all checks in the prescribed sequence for the instrument. Repeat the check sequence at least three times but do NOT make an adjustment unless the same check indicates the same amount of error every time. 8. Remember that most tests show an error that is double the actual displacement error in the instrument. Be especially watchful for creep, that is, a change in position caused by settlement or by temperature change in the instrument. To detect any possible creep, allow every set bubble or line of sight to stand for a few seconds and ensure that no movement occurs during the interval. Before making an adjustment, consider whether any error discovered will have a material effect on field results. Make any adjustments in a prescribed order. After making an adjustment, retighten the adjusting parts firmly but not too tightly, then repeat the original check, and readjust if necessary. After making all contemplated adjustments, repeat the entire round of checks in the proper order. This will indicate whether an initial adjustment has been disturbed by a subsequent adjustment. The following sections will address field tests and adjustments for the engineer’s level and the transit. While the principles of performing adjustments are nearly the same for one manufacturer’s level or transit as compared to another manufacturer’s, there are some differences in detail. Therefore, when preparing to adjust an instrument, always consult the operator’s manual for that particular instrument. When a particular surveying requires a high degree of accuracy, the level or transit you use must be in perfect adjustment. In this event, you must perform the tests presented in the following sections and make any necessary adjustments. However, when the survey can tolerate lower accuracy, you can usually compensate for maladjustment until a proper adjustment can be made. Following each of the next instrument-adjustment discussions, a note will present a method of compensating for maladjustment. Keep in mind, however, that if you frequently check your instruments and keep them in good adjustment, these compensations should seldom be necessary. 2.1.2 Self-Leveling Level Adjustments The self-leveling level (also called automatic level) shown is Figure 17-5 is a precise, time-saving development in leveling instruments. It did away with the tubular spirit level, whose bubble takes time in centering as well as in resetting its correct position from time to time during operation. 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 center the bubble of the bull’s-eye level approximately. 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 NAVEDTRA 10469A 17-8 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. 2.1.3 Theodolite A theodolite is essentially a transit of high precision. Theodolites come in different sizes and weights and from different manufacturers. Although theodolites may differ in appearance, they are basically alike in their essential parts and operation. Some of the models currently available for use in the military are WILD® (Herrbrugg), BRUNSON®, K&E® (Keuffel & Esser), PATH®, and Trimble® theodolites. To give you an idea of how a theodolite differs from a transit, we will discuss some of the most commonly used theodolites in the U.S. Armed Forces. 2.1.3.1 One-Minute Theodolite The one-minute directional theodolite is essentially a directional type of instrument. This type of instrument can be used, however to observe horizontal and vertical angles as a transit does. The theodolite shown in Figure 17-6 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. The main or essential parts of this type of theodolite are discussed in the next several paragraphs. Figure 17-5 – Example of self-leveling level. NAVEDTRA 10469A 17-9
• Horizontal Motion – Located on the lower portion of the alidade, and adjacent to each other, are the horizontal motion clamp and tangent screw 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, you should use the circle clamp only to set the initial reading. You should set an initial reading of 0°30´ on the plates when a direct or reverse (D/R) pointing is required. This will minimize the possibility of ending the D/R pointing with a negative value.
• 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. The telescope can be rotated in the vertical plane completely around the axis (360°).
• Levels – The level vials on a theodolite are the circular, the plate, the vertical circle, and the telescope level. 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 45° 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, as shown in Figure 17-7. The telescope level, mounted below the telescope, uses a prism system and a 45° mirror for leveling operations. When a telescope is plunged to the reverse position, the level assembly is brought to the top. Figure 17-6 — Wild® oneminute theodolite. NAVEDTRA 10469A 17-10
• 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 the shortest focusing distance of 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 (Figure 17-8). This circle covers 31 min of arc and can be imposed on the sun’s image (32 min 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. The amount of illumination for the telescope can be adjusted by changing the position of the illumination mirror. Figure 17-7 – Coincidence type level. Figure 17-8 – Theodolite reticle. Figure 17-9 – Three-screw leveling head. NAVEDTRA 10469A 17-11
• 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 (Figure 17-9). 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.
• 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. In the degree-graduated scales the images of both circles are shown as they would appear through the microscope of the one-minute theodolite (Figure 17- 10). Both circles are graduated from 0° to 360° with an index graduation for each degree on the main scales. This scales graduation appears to be superimposed over an auxiliary that is graduated in minutes to cover a span of 60 min (1°). The position of the degree mark on the auxiliary scale is used as an index to get a direct reading the degrees and minutes. If necessary, these scales can be interpolated to the nearest 0.2 min 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 a zenith distances and not vertical angles. Figure 17-11 shows how these zenith distances can be converted into vertical angles. In the mil-graduated scales, the images of both circles are shown as they would appear through the reading microscope of the 0.2-mil theodolite (Figure 17-12). 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. The auxiliary scales are graduated from 0 to 10 roils in 0.2-mil increments. Readings on the Figure 17-11 – Converting zenith distances into vertical angles (degrees). Figure 17-10 – Degree-graduated scales. NAVEDTRA 10469A 17-12 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. These zenith distances can be converted into vertical angles as shown in Figure 17-13. 2.1.3.2 One-Second Theodolite The one-second theodolite is a precision direction type of instrument for observing horizontal and vertical directions. This instrument is similar to, but slightly larger than the one-minute theodolite. The WILD® theodolite is compact, lightweight, dustproof, optical reading, and tripod-mounted (Figure 17-14). It is one spindle, one plate level, a circular level, horizontal and vertical circles read by an optical microscope directly to 1 sec (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 that of the one-minute theodolite, including the horizontal and vertical motions, the levels, the telescope, the tribrach, and the optical system shown in Figure 17-15. The main difference between the two types, besides precision, is the manner in which the circles are read. The circle to be viewed in the one-second theodolite is selected 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-min 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 Figure 17-16. The numbers increase in value 0° to 360°, clockwise around the circle. The coincidence knob on the right side of, and near the top of, the right standard is used in reading either of the circles. The collimation level and its tangent screw are used when the vertical circle is read. Figure 17-12 – Mil-graduated scales. Figure 17-13 – Vertical angles from zenith distances (mils). NAVEDTRA 10469A 17-13 Figure 17-14 — One-second theodolite. Figure 17-15 — Circle-reading optical system. NAVEDTRA 10469A 17-14 The circles of the theodolite are read by the coincidence method in which optical coincidence is obtained between diametrically opposite graduations of the circle by turning the micrometer or coincidence knob. When this knob is turned, the images of the opposite sides of the circle appear to move in opposite directions across the field of the circle-reading 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 that are to be used in making the coincidence. The index mark will be either in line with a circle graduation or midway between two graduations. The final coincidence adjustment should be made between the graduations in line with the index mark or when this index mark is halfway between the two closest graduations.
• Horizontal Circle – To read the horizontal circle, turn the inverter or circleselector knob until its black line is horizontal. Adjust the illuminating mirror to give uniform lighting to both sections of the horizontal circle; the micrometer scale is viewed through the circle reading microscope. Focus the microscope eyepiece so that the graduations are sharply defined. The view through the microscope should then be similar to Figure 17-16, view A. From this point continue the following way: o Turn the coincidence knob until the images of the opposite sides of the circle are moved into coincidence. Turning this knob also moves the micrometer scale. The view through the microscope now appears as shown in Figure 17-16, view B. o 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. In Figure 17-16, view B, there are five divisions between 105 and 285; and the reading, therefore, is 105°50´. The index may also be used for direct reading of the tens of minutes. Each graduation is treated as 20 min. Thus, the number of Figure 17-16 — View of a one-second theodolite circle. NAVEDTRA 10469A 17-15 graduations from the degree value to the index mark multiplied by 20 min is the value. If the index falls between graduations, another 10 min is added when the tens of minutes is read directly. o Read the unit minutes and seconds below from the image of the micrometer scale. This scale has two rows of numbers below the graduations; the bottom row is the unit minutes and the top row, seconds. In Figure 17-16, view B, the unit minutes and seconds are read as 7´23.5˝. o Add the values determined in steps 2 and 3 above. This gives 105°57´23.5˝ as the final reading.
• 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. You then go on in the following way: o Use 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 (Figure 17-17). o Read the vertical circle and micrometer scale as described before. Be sure to have proper coincidence before you take the reading. o The vertical circle graduations are numbered to give a 0° reading with the telescope pointing to the zenith. Consequently, the vertical circle reading will be 90° for a horizontal sight with the telescope direct and 270° for a horizontal sight with the telescope reversed. Figure 17-17 shows the view in the circle-reading microscope for direct and reversed pointings on a target. These readings are converted to vertical angles as follows: Telescope Direct Telescope Reversed Circle Reading 86°17´43.5˝ 273°42´21.5˝ Zenith Distance 86°17´43.5˝ 86°17´38.5˝ Mean Zenith Distance 86°17´41.0˝ Mean Vertical Angle + 3°42´19.0˝ NAVEDTRA 10469A 17-16 There are two separate occasions for setting the horizontal circle of the theodolite. In the first case, the circle is set 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, the circle is set as follows: Set the micrometer scale to read the unit minutes and the seconds of the given values. Then, with the circle-setting knob, you turn the circle until coincidence is obtained at the degree and tens of minutes value of the given reading. This setting normally can be made accurately to plus or minus 5 sec. After the circle is set in this manner, the actual reading should be determined. In the second case, the circle is set to a value of a given angle. When a predetermined angle is measured, you 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, you turn the instrument in azimuth and make coincidence at the degrees and tens of minutes value that is to be set. The predetermined value can usually be set on the circle in this way to plus or minus 2 sec. 2.1.4 Total Station (Trimble® 5600) Adjustment The Trimble® 5600 Total Station when used with the Trimble® Alphanumeric Control Unit (ACU) and Trimble® Integrated Survey Rover (ISR) gives you the best and most productive measuring method available today for every measuring situation. In this section you will be introduced to the components of the Total Station and their adjustments. The Trimble® 5600 Total Station, Trimble® ACU, and ISR are used with the Terramodel programs which are loaded to a base computer and can be downloaded to the ACU for known or unknown control points. Upon completion of your survey or measurements the data can be downloaded from the Trimble® ACU back to the base computer for creation of linework or other layout as desired (Figure 17-18). Figure 17-17 – View of a vertical circle for direct and reversal pointings. NAVEDTRA 10469A 17-17 2.1.4.1 Tripod Adjustment The following steps are to be followed when setting up the tripod over a control point and making adjustments:
• Unwrap the tripod and extend its legs so that the tripod head is at approximately chin level (higher is better for more precise work, so that you can get maximum leg spread). Spread the tripod legs over the initial occupied point so that the tripod head is approximately level. Make sure the legs are spread as widely as practical for maximum stability.
• Attach the instrument tribrach to the tripod head and ensure that the tribrach’s leveling foot screws are centered half way between their range of movement (for ease of leveling). Hand tighten the bayonet screw at the base of the tribrach. Step or “set” one leg into the ground securely (usually the leg opposite the sight on your tribrach), sight through the optical plummet, and pick up and move the other two tripod legs until the cross hairs are centered over your occupied point nail or marker. (You can place the toe of your shoe near the point for reference.) NOTE If the tribrach crosshairs are out of focus, adjust the crosshairs ring first until the crosshairs appear clear and crisp. Then, adjust the focus ring until the image is in focus. To check for parallax, slowly move your head around while looking Figure 17-18 – Data flow using Trimble® 5600 Total Station. NAVEDTRA 10469A 17-18 through the optical plummet. You should see not movement between the crosshairs and the focused background (this is known as being out of parallax), nor should the crosshairs move apart.
• Once the crosshairs are within one centimeter of the point (1/2”), step the remaining two legs into the ground.
• Precisely position the tribrach crosshairs over the point by using the leveling foot screws on the tribrach.
• Level the bull’s-eye bubble on the tribrach by using two tripod legs. Do NOT level using the tribrach foot screws. At this point you are leveling the tripod head. When the bubble is within the circle of the bull’s-eye. Use the tribrach leveling foot screws to precisely center the bubble.
• Once the bull’s-eye bubble is precisely level, look through the optical plummet to ensure that the crosshairs are over the point or at least within a couple of centimeters (1”). Center the crosshairs precisely over the point by loosening the tripod bridge screw and gently slide the tribrach and adapter over the point. Be sure not to rotate the tribrach. When the crosshairs are centered on the point, tighten the tripod head screw. If the tribrach overhangs the tripod head, return to the step where the tripod legs were spread over the initial occupied point and adjust. NOTE You can check the set up and calibration of your tribrach by attaching a plumb bob to the tripod head screw so it hangs over the point. It should hang precisely over the point ± the plumb bob string width. If the wind is blowing, you may want to perform this tribrach check indoors.
• Check the level bubble. If the level is out just a little, return to the step where the bubble is within the circle of the bull’s-eye and use the tribrach leveling foot screws to precisely center the bubble. If it is out more than a couple of millimeters, redo the step where you precisely positioned the tribach crosshairs over the point by using the leveling foot screw on the tribach. 2.1.4.2 Attaching and Leveling the Trimble®/Geodimeter Total Station The following steps should be followed when attaching and leveling the Trimble®/Geodimeter Total Station (Figure 17-19):
• Remove the instrument from its case and loosen the horizontal motion lock. Rotate the base of the instrument until the RS-232 port aligns with the notch in the tribrach. Gently place the instrument in the tribrach and be sure to lock it in place by turning the tribrach locking knob clockwise until it stops.
• Check the bubble on the optical plummet and re-level if needed. Then, recheck to be sure the crosshair of Figure 17-19 – Trimble®/Geodimeter Total Station with ACU NAVEDTRA 10469A 17-19 the optical plummet is still centered over the point. If required, loosen the bayonet screw of the tribrach and move it over the point (again, taking care not to rotate the tribrach as you move it). Rotate the instrument so its keyboard is parallel to two of the tribrach foot screws.
• Turn on the instrument by pressing the power key at the lower left corner of the keyboard.
• Use the tribrach’s two foot screws to center the cursor between the two of the display lines. Remember that the bubble goes in the direction of your left thumb. Without rotating the instrument, use the third foot screw to center the top cursor between the other two display lines. When both cursors are centered, the instrument is correctly leveled in coarse mode.
• Press the Aim/Measure (A/M) button. The instrument will now automatically adjust and engage its dual axis compensator. You should have a prompt of “Temp =. Use your thermometer and input the current temperature. At the “Press =” prompt, use your barometer and input the correct barometric pressure. At the “Offset =” prompt, input 0 (zero) if you are using standard Geodimeter/Trimble® glass of prisms. Use an offset of 2mm or 0.00656 feet for a 360° prism.
• At the “HA Ref =” prompt, simply press the Enter (ENT) key. You will most likely be inputting an actual value.
• The instrument is now in Program 0 mode and the top of the display should read STD P0 TIME and is ready for fine leveling, collimation, or to run a program.
• Adjust the display contrast for the best possible viewing for current lighting conditions by using the Menu (MNU 13) Key. NOTE Continue with the next steps only if you are going to do a precise survey. If you are just running a topo survey, for example, you are finished with this setup procedure.
• For a precise survey you would turn the instrument so it is parallel to two of the tribrach foot screws and fine level it by pressing the fine level button which is marked with a level symbol; which is the same key as button “N” in alpha mode.
• Once the indicators are both centered, using the fine leveling, press the fine level button again. As long as your measurement units are correct and the instrument has been collimated, you are now ready to begin collecting survey data by running precise survey programs which will be discussed later. 2.1.4.3 Trimble® Alphanumeric Control Unit (ACU) If you want to switch between using the Trimble® ACU and another control unit Trimble® strongly recommends that before each switch you perform the following adjustments which are described in detail in the Trimble® 5600 user manual:
• Horizontal collimation
• Vertical collimation
• Compensator run center The internal battery of the Trimble® ACU can provide up to one hour of stand-by time to avoid any potential data loss should your external power source expire. The internal battery powers the Trimble® ACU only. It does not power any device that may be NAVEDTRA 10469A 17-20 connected. The Trimble® ACU is configured by default not to run on internal battery power for users with the Windows CE operating system version 4.0.9 or later. To enable the Trimble® ACU to run from internal battery power perform the following steps:
• From the start menu, select “Settings/Control Panel” and then click the power icon.
• In the “Run On Battery” tab, select the “Enable running on Internal Battery” check box.
• Now the Trimble® ACU will run from internal battery power. NOTE Under no circumstances should you rely on the internal battery for extended periods, especially during data collection. When the Trimble® ACU is running on its internal battery (when enabled), Trimble® recommends that you connect an external power source immediately. External power sources include the Trimble® ACU mains charger, the Trimble® 5600 Total Station and the CU holder for robotic surveying. To toggle the backlight on and off, press the “Shift” button, and then press the “Trimble®” button. To access the backlight settings, from the “Start” menu select “Settings/Control Panel” and then click on the “Display” icon. Use the “Alpha” key to enter alphabetic characters on the Trimble® ACU. Press this key to switch between alpha and numeric modes. To enter an upper case character in the preview panel, press the “Shift” key while in alpha mode. To use the Trimble® ACU with a Trimble® 5600 Total Station, the instrument must have firmware version 696-03.05 or later installed. To start the system, use the following procedure:
• Set up the instrument and ensure that the Trimble® ACU is turned off, and then attach it to the front of the instrument. Connect a power suppkly to the footconnector of the instrument.
• Press the green power button on the Trimble® ACU to start the system. The instrument should beep indicating that it has been turned on. You will then be able to use the survey application software installed on the Trimble® ACU to connect to the instrument and start your survey. To use the Trimble® ACU with a Trimble® Integrated Survey Rover (ISR) (Figure 17- 20) the following procedures should be used:
• Attach the Trimble® 5800 RTK Rover and the Trimble® ACU holder to the rod. Insert a freshly charged battery in the Trimble® 5800 GPS Rover, and then press the green power button to turn it on.
• Attach two freshly charged batteries to the Trimble® ACU holder. Ensure that the Trimble® ACU is turned off, Figure 17-20 – Trimble® 5800 RTK Rover with ACU NAVEDTRA 10469A 17-21 and then attach it to the Trimble® ACU holder.
• Press the green power button on the Trimble® ACU to start the system. You will then be able to use the survey application software installed on the Trimble® ACU to connect to the receiver and start your survey.
2.2.0 Minor Repairs and Replacement Procedures Minor repairs to surveying instruments and equipment are those that can be done in the field with the use of simple tools. Major repairs must be done by instrument specialists generally employed by the manufacturers of the instruments. Never attempt to make a major repair yourself. 2.2.1 Repair It or Replace It? Whether you or someone else in the unit should attempt to repair a damaged item of equipment will depend on the nature of the damage and the character of the item. For example, you can easily splice a broken tape, but should you attempt to straighten a bent compass needle? That decision would depend on the type of compass: an ordinary pocket compass, perhaps yes, the compass on a transit, probably no. Damage to articles such as range poles, tripod legs, and the like may be easily repaired in a battalion or PWD shop, and minor damage to instruments may be repaired occasionally as well. However, major repairs to instruments, if economically worthwhile, should be done by manufacturers, their authorized representatives, or competent Navy instrument repairmen. If the senior engineering tech or engineering officer deems an instrument beyond economical repair, it must be surveyed (properly disposed of) using standard survey procedures. Then a replacement instrument can be ordered through the Navy supply system. Expendable items are procured in the same manner. 2.2.2 Navy Supply System The Navy supply system lists, identifies by a stock number, and describes in a stock catalog each item of equipment or supply that is available. A battalion allowance list identifies items that may be drawn from supply, and indicates the maximum number permissible. When a battalion’s inventory falls short of the allowance due to expenditure, wear, casualty, loss, or some other type of attrition, the shortage must be replaced. The battalion or PWD shop personnel may be able to replace some items such as range poles, chaining pins, bull-points, turning-point pins, targets, stake bags, equipment boxes, and the like, but most items are replaced by supply from the nearest available naval supply depot. To replenish an item, you must order it by stock number and follow a prescribed procedure. To learn the correct procedures, contact one of the supply petty officers in the unit or study the chapters on the Navy supply system in Military Requirements for Petty Officers Third and Second Class, NAVEDTRA 14504. 2.2.3 NMCB Surveyor’s Kit Every NMCB is outfitted with adequate surveying supplies and equipment. They are listed in the NMCB Table of Allowance (TOA) and contained in Surveyor Kit #80010. Normally, four complete kits are carried in the battalion allowance and available for checkout to the surveyor section supervisor or the senior engineering tech. NAVEDTRA 10469A 17-22 Each survey party chief is responsible for making sure the kit assigned to the crew is complete. In addition, the kits must be inventoried during turnover and at twice-monthly intervals throughout deployment. The purpose of these inventories is to ensure both 100% accountability and a proper state of good repair of the items in the kit. Remember, if you have custody of the kit, you can be held financially accountable for items missing or damaged through negligence. Most consumable items in the kit, such as pencils, pencil leads, lumber crayon, and surveyor’s flagging, are stocked in the battalion supply department for kit replenishment. Additional supplies and equipment are also stocked in the engineering office surveyor’s locker to supplement the kits. Summary Seabees operate in many different environments under a wide range of circumstances while upholding the “Can Do” motto. The engineering survey is often the first step in beginning a project, and the quality of the survey will depend on the skill of the survey crew functioning with properly maintained and adjusted equipment. As an engineering technician, being familiar with equipment maintenance and comfortable with adjustments after a thorough systematic check will enable you to support both your unit and the tradition. (Figure 17-21) Figure 17-21 — Seabees operating multiple survey equipment under varied environments. NAVEDTRA 10469A 17-23
Review Questions
6HOHFWWKH&RUUHFW5HVSRQVH 1. Which of the following definitions best describes “adjustment” as presented in Chapter 17? A. Aligning the fixed parts of the instrument B. Aligning the telescope for leveling work C. Aligning the instrument for a level run D. Aligning a transit scope for use with a level 2. Which, if any, of the following items comes with an instrument to assist you with care and maintenance? A. A tool kit to repair the instrument B. A prepaid shipping box to return it to the manufacturer for repairs C. A user’s manual D. None of the above 3. Which of the following situations should you avoid when handling or caring for your instrument? A. Setting up the instrument in a street B. Removing the instrument from the case by the telescope C. Tightening the instrument to the tripod head during setup D. Tightening all screws to a firm bearing 4. What is the preferred method for carrying an instrument on a sidehill? A. On the uphill shoulder B. In front of you with the tripod legs extended C. Under the arm on the downhill side D. On the downhill shoulder 5. All clamp screws should be firmly tightened when an instrument is transported. A. True B. False 6. In what manner should you store an instrument when not in use? A. In the carrying case B. On a shelf in the survey locker C. Mounted on the tripod D. Any place that is convenient NAVEDTRA 10469A 17-24 7. Which of the following bags may be used to carry stakes and hubs? A. Canvas bag with a shoulder strap B. Newsboy’s bag C. Seabag D. All of the above 8. What is the recommended method for carrying surveyor’s tacks? A. In the tack box B. In a pocket on the surveyor’s bag C. Stuck in a rubber ball or piece of soft wood D. In your shirt pocket for quick access 9. You should NEVER carry any equipment in sheaths or pouches, or on your belt. A. True B. False 10. You have been surveying and caught in the rain. What should you do with the instrument upon return to the office? A. Store the instrument in the carrying case. B. Blow-dry the instrument with a hair dryer. C. Wipe it down with a cloth. D. Remove it from the case and dry the instrument at room temperature. 11. You should clean the lens of the telescope with a chamois or lintfree cloth only. A. True B. False 12. What type of lubricant is recommended for lubricating transits in subzero temperature? A. Watch oil B. Whale oil C. Graphite D. 10W-30 13. Which of the following sources should you consult before doing anything to an instrument? A. Tech library B. Senior engineering tech C. Manufacturer’s manual D. Either B or C NAVEDTRA 10469A 17-25 14. Why is it important to clean mud and dirt from your equipment after use? A. To prevent rust or decay B. To ensure neatness C. To keep the Chief happy 15. Why is it important to take good care of your equipment? A. For inspection purposes B. For quality work and accurate surveys C. Both A and B above D. For safety 16. Major repairs and major adjustments are among the responsibilities of the engineering tech. A. True B. False 17. Recalibration should be done by whom? A. Senior engineering tech B. Manufacturer C. Supply department D. Instrumentman 18. Which of the following skills should the surveyor possess in order to make proper adjustments? A. Ability to tell the effect of the adjustment on other parts B. Ability to perform tests used to determine when the instrument is out of adjustment C. Knowledge of the proper sequence for making adjustments D. All of the above 19. Which of the following instrument parts is/are used to make instrument adjustments for levels? A. Tripod head B. Cross hairs C. Level tubes D. Both B and C above 20. The cross hairs on a telescope are out of adjustment when they fail to align with _____. A. the object being sited B. one another C. the optical axis D. the alignment points NAVEDTRA 10469A 17-26 21. How do you determine if an Abney or Locke level is out of adjustment? A. Check the reflected bubble with the instrument in a horizontal plane. B. Check the reflected bubble with the instrument in a vertical plane. C. Check the plate level bubbles. 22. What is a general rule regarding the frequency of adjustment? A. Check and adjust often. B. Check rarely and adjust rarely. C. Check often and adjust rarely. D. Check rarely and never adjust. 23. You feel your instrument is out of adjustment. Which of the following procedures should you do before making any adjustments? A. Ensure the instrument is screwed down on the tripod. B. Set the instrument up in the shade. C. Repeat the checks at least three times. D. All of the above 24. What type of surface should you use to set up an instrument for adjustment? A. Asphalt B. Chipped hardened surface C. Sand D. Plywood 25. What purpose, if any, does retightening the wing nuts on the tripod legs accomplish? A. To prevent a possible shifting of the legs B. To ensure the nuts did not loosen themselves C. To keep the tripod head from moving D. None 26. What amount of the actual displacement error do most tests show an error equal to? A. Half the actual error B. Double the actual error C. Equal to the actual error D. Three times the actual error 27. What is creep in relation to the instrument? A. Position shift due to heat B. Settlement of the instrument C. Position shift due to cold D. All of the above NAVEDTRA 10469A 17-27 28. The operator’s manual is your first source of information when instruments need adjustment. A. True B. False 29. You are performing a survey requiring a high degree of accuracy. Which, if any, of the following procedures should be one of the first steps you perform? A. Check your instrument for maladjustment. B. Figure the compensation for adjustments to the instrument. C. Oil the tripod head. D. None of the above 30. You are assigned to a survey party. You get the level along with your other equipment. What procedure, if any, should you perform on the instrument before starting work? A. Check the instrument for proper adjustment. B. Adjust all the bubble tubes to the maximum angle. C. Perform a two–peg test. D. None 31. When adjusting a level, you should follow an exact order for making all the adjustments. A. True B. False 32. You have found the level tube out of adjustment on a level. You set the instrument up and then level the bubble over each set of leveling screws. What is your next step? A. Rotate the instrument 90° and adjust the bubble half the distance to the center of the tube. B. Rotate the instrument 180°, check the bubble, and adjust the bubble to the center of the tube. C. Rotate the instrument 180° and adjust the bubble half the distance to the center of the tube. D. Rotate the instrument 180°, loosen the capstan screws, and rotate the reticle until the bubble is half the distance of the tube. 33. In what order should adjustments on a level be made? A. Vertical cross hair, level tube, and line of sight B. Horizontal cross hair, line of sight, and level tube C. Level tube, line of sight, and horizontal cross hair D. Level tube, horizontal cross hair, and line of sight NAVEDTRA 10469A 17-28 34. The telescope of the one-minute theodolite is an inverted image type. A. True B. False 35. The tribrach assembly found on most one-minute theodolite units contains which of the following parts? A. Leveling screw B. Circular level C. Optical plumbing device D. All of the above 36. What degree does the vertical circle read when the theodolite’s telescope is pointed straight down? A. 0° B. 90° C. 180° D. 270° 37. What method of reading the circles is used on the one-second theodolite? A. Direct B. Coincidence C. Horizontal D. Vertical 38. Which of the following activities may perform minor repairs? A. Navy cal lab B. Local PWD C. Battalion machine shop D. All of the above 39. When a piece of equipment is damaged beyond repair, it must be replaced. From what source may you obtain a replacement? A. PWD B. Equipment manufacturer C. Army/Navy surplus store D. Navy supply system 40. What source/reference determines the maximum number of any item allowed in a battalion? A. Supply department B. Table of Allowance C. Authorization list D. Naval supply depot NAVEDTRA 10469A 17-29 41. Which of the following sources should you refer to when checking on the quantity of surveying kits in a battalion? A. Table of Allowance B. 80010 inventory list C. Military Requirements for Petty Officer Third Class D. NAVFAC P-315 NAVEDTRA 10469A 17-30 Trade Terms Introduced in this Chapter Reticle A grid or pattern placed in the eyepiece of an optical instrument, used to establish scale or position. NAVEDTRA 10469A