Measurement and Geospatial Data Acquisition
This domain tests field procedures and quality control for total stations, GNSS, and differential leveling. The exam expects instrument knowledge tied to acceptable accuracy, not button-pushing.
Total station and leveling
A traverse should begin and end on known control, with checks on angular and linear closure. EDM work requires correct prism constants and atmospheric corrections. Differential leveling requires a closed loop or a check between known benchmarks; misclosure is compared with the project tolerance before adjustment. Rod plumb, turning-point stability, and equal foresight/backsight distances reduce systematic error.
GNSS
RTK GNSS requires a fixed solution, adequate satellite geometry, and an independent check on known control. Do not treat a autonomous or float solution as survey quality. GNSS-derived coordinates are typically grid coordinates; ground distances require the combined factor. Kentucky’s State Plane Coordinate System is a single zone using a Lambert Conformal Conic projection on NAD83. Know whether the project is in meters or U.S. survey feet and record the datum and epoch.
Worked example
A level loop over 2,000 feet closes with +0.048 foot. The project tolerance is 0.05 ft√M. M = 2,000 ÷ 5,280 = 0.379 mile; √M = 0.616; allowable = 0.05 × 0.616 = 0.031 foot. Because 0.048 exceeds 0.031, the loop fails and must be reobserved or investigated. The reasoning is to compare misclosure in the correct units and form before adjusting anything.
Traps
Mixing grid and ground distances, accepting RTK without a check shot, using the wrong prism constant, and ignoring atmospheric corrections are frequent mark-losers.