Work Element Two: Field equipment and Instruments

When setting up a surveying tripod on a hillside the best practice is to?

Place one shortened leg uphill

To check whether the compensator on an auto-level is working, the user should?

Press the button release on the instrument (if it has one) or tap on the instrument lightly to ensure the compensator is free

Surveying equipment is...

• Equipment used in stressful conditions - extreme weather, dusty construction areas, bumpy transportation, etc. • Proper care is required during use, storage, and transportation of the equipment to properly execute a successful survey • Not doing so increases replacement cost of equipment, and seriously jeopardize the efficiency, accuracy, and profitability of the survey

Transportation

►A major portion of equipment damage can occur when placed into or taken out of the survey vehicle • Place heavier items lower in the back of the truck • Place tools so they don't jostle against ►Never "shoulder" a total station while mounted on the tripod - total station should always be moved in the carrying case • Weight of the total station could cause the center spindle to snap or bend

General Principles

►All equipment should be kept as clean and dry as practicable, especially if storing for any length of time ►Wooden surfaces should be wiped clean of caked mud and moisture ►Metal surfaces should be cleaned and wiped as dry as practicable • A light coat of oil should be applied to metal tapes to prevent rusting during storage, excess oil should be wiped off

Collimation of Total Stations

►Collimation Error occurs when the line of sight is not aligned with the true horizontal line (vertical error) or with the vertical axis perpendicular (horizontal error) ►Collimation Adjustment is made to correct this and should only be done by an authorized repair shop

Electronic Distance Measurement (EDMs)

►Electronic Distance Measurement (EDMs) • Measured Distance only • Uses beam of light

Gunters Chain

►Gunter's Chain • 66 feet long • 100 links • 1 link = 7.92 in • 80 chains = 1 mi

Hand Held Radios

►Modern survey equipment and techniques have made the hand held radio an essential part of a survey crew's equipment ►They are ruggedly built but require special care and maintenance in accordance with owner's manual ►Batteries are primary source of problems with hand held radios

EDMs & GPS

►Most distance measuring devices use electronic instrumentation which require some level of calibration ►EDM's should be checked against a NGS Calibrated Baseline at least once a year. ►Total Error = Fixed Error + parts per million

Surveyors Compass

►Surveyor's Compass • Pike & Son 1831-1849 • Measures Horiz Angles • Magnetic Bearings • Upright Sights • Mostly Brass

Tribrachs

►Tribrachs are the detachable base for all theodolites, total stations, forced centering targets, and EDM's ►Equipped with a bull's eye bubble and optical plummet for setting up precisely over the survey mark ►Allows the surveyor to "leapfrog" between the backsight, instrument point, and foresight which increases the speed, efficiency, and accuracy of the survey ►Tribrachs should be attached to the tripod first so the instrument setup is easier, and safer

Temperature corrections are applied to?

measurements made using a steel tape.

How often should an EDM be calibrated at a baseline?

once a year as needed

What should you do if you detect that your instrument has a collimation error?

take it to a qualified repairman

Survey grade GPS receivers are capable of greater positional accuracy than recreational GPS receivers due to?

-dual-frequency capability. -have multiple channels for satellite tracking. -being able to measure both code and carrier phase signals.

It's okay to carry a theodolite or total station horizontally.

False

The purpose of a peg test is to?

check that the line of sight of a level is correct.

A user should check and adjust tribrachs and rod levels.

true

Care of Total Stations

►Although instruments are ruggedly built, careless or rough use and unnecessary exposure to the elements can cause serious damage ►Lifting - instruments should be removed from the case with BOTH hands. One hand should grab the handle while the other supports the base. One hand should remain holding the instrument until the tribrach or tripod spindle are engaged ►Carrying a tripod - In most cases, the instrument should be removed and re-cased for transportation to a new setup. If the new point is nearby, the instrument should be carried in the vertical position (tripod legs pointing straight down). An instrument should never be shouldered or carried horizontally

Tapes

►Available in various lengths, material, and graduations ►EDM's have replaced the need for tapes over long distances they are still useful for small scale work ►Care of Tapes • Keep tape flat and straight • Avoid pulling on loops which can quickly become a kink and snap the tape • Do not pull tapes around poles or other objects which can cause the tape to be stretched or snap • Do not wind tapes up to tight - could stretch on the reel • Wipe clean and dry at end of day, oil lightly to prevent rust • Avoid storing in damp place

Batteries

►Batteries will lose their ability to hold a charge over time due to the frequent partial discharge/ recharge cycle ►Low temperatures will also decrease batteries ability to hold a charge ►Occasionally batteries should be completely discharged before recharging ►If batteries completely fail they should be re-celled or replaced

Bull's Eye Rod & Pole Levels

►Bull's eye level is used for maintaining both level rods and sighting poles in a vertical position. An out of adjustment Bull's eye level can cause accumulative errors ►Simple method for checking level is to check it against a previously checked door jamb or permanent building part ►Other, more elaborate, checking procedures can be developed using plumb lines or other devices

Care of Tools

►Improperly maintained tools can be a source of annoyance, as well as being a safety hazard. Each employee is responsible for keeping their tools in good condition. Avoid laying small tools on the ground where they can become easily lost ►Repair or replace any driving tool that is burred or fractured on any part of the striking face as it may create "shrapnel" ►Crooked or warped handles can cause injury as well and should be replaced immediately. Handles should be firmly secured on all cutting and driving tools

Automatic Levels

►Line of sight is maintained perpendicular to the direction of gravity through a system of prisms, called a compensator ►Easily maintained ►Protect from dust - dust can cause the compensator to hang up ►Frequently check the bull's eye level ►To check the compensator use the push button release while looking through the scope - if it bounces freely the compensator is working, if not send it to an authorize repair shop

Field Adjustments

►The party chief should develop a set of test procedures to be used frequently for elimination of gross errors. Such tests should include a check of items including levels, optical plummet, and tripod. In the field, adjustments should only be made when the instrument results are poor or require excessive manipulation ►Each instrument should be periodically checked and serviced in a controlled environment.

Theodolite

►Theodolite • Measures angles only

Transit

►Transit • A surveyors compass with a telescope • Could be flipped for BS & FS • Rugged • Could take readings with or without the needle • Big advancement in survey equipment

Care of Tribrachs

►Tribrachs are an integral part of the precision equipment and should be handled accordingly ►They should be transported separately in cases to protect the machined base surface, bulls eye level, and optical plummet eye piece ►Do not over tighten the spindle which can cause excessive pressure on the leveling plate ►Although leveling screws are covered, dirt or dust can work into the threads and cause wear. Carefully disassemble, clean, and lubricate with light instrument oil. This should only be done in a shop by experienced personnel

Adjustment of Tribrachs

►Tribrachs not in adjustment can cause small random errors and should be checked often ►Quick adjustment can be done with a plumb bob ►More accurate adjustment is to rotate the tribrach 120 degrees over a smooth surface. For the first sighting outline the tribrach base with pencil, level, then mark the center. Rotate 120 degrees, level, and mark the center. Repeat a third time. • If the tribrach is out of adjustment you will see 3 separate dots at the center • Adjust the plummet to sight the center of the 3 points • Repeat test to verify the adjustment

Routine Care

►Visually inspect equipment daily for cracks, bumps, and dents ►Check machined surfaces and polished faces of the lens and mirrors ►Try the clamps for smooth operation, absent binding or gritty sound ►Wipe down exterior of equipment often ►Dirt and dust should be removed only with a clean soft cloth or with a camel hair brush ►Cover the instrument when not in use, especially on dusty construction sites or in moist conditions ►Close instrument case when not removing or packing up the gun - dust will likely settle on the inside of the case and cause harm to the instrument while stored in the case

Zenith Circle

►Zenith Circle • Mostly used for celestial observations

The best way to ensure a stable tripod setup on level ground is to?

Lightly step on each leg to ensure firm footing.