Measurement Technology and Field Procedures
What this domain tests
This domain tests field procedures and the checks that make measurements defensible: instrument setup, redundancy, and closure.
Core rules
- Total stations require checks for collimation, prism constant, atmospheric correction, and centering. Record the instrument and prism heights and the basis of bearings.
- GNSS RTK needs a fixed solution, adequate satellite geometry, a base or network tie, and an independent check on a known point. A single fixed shot is not a boundary measurement.
- Differential leveling uses backsight and foresight readings; the height of instrument changes each setup. Close loops or run between known benchmarks.
- Traverses should have redundant angles and distances; compute angular and linear closure before adjusting.
Worked example
A five-sided closed traverse has a measured interior-angle sum of 540°00′45″. The theoretical sum is (n − 2) × 180° = 3 × 180° = 540°00′00″. The angular misclosure is +45″. With five angles, apply −9″ per angle if distributing equally. If the perimeter is 2,500.00 ft and the linear closure is 0.10 ft, the closure ratio is 2,500.00 ÷ 0.10 = 1:25,000. Report the method and adjusted coordinates, not just the raw field notes.
Traps
Accepting one RTK fix; ignoring prism constant or atmospheric correction; poor tripod centering; failing to check a known point; and adjusting a traverse before identifying a blunder.