Measurement Technology and Field Procedures
What this domain tests
Instrument use, field checks, error sources, GNSS, total stations, levels, and coordinate systems. Maine work commonly uses the Maine State Plane Coordinate System, NAD83, East and West zones.
Core rules
- Establish control, then check it. A backsight or resection is not a substitute for an independent check.
- Total-station errors include centering, leveling, collimation, prism constant, and atmospheric correction.
- GNSS-RTK requires a fixed solution and adequate satellite geometry; repeat observations and check against a known point.
- Keep field notes that identify instrument, operator, date, weather, monument condition, and observations.
- Distinguish ground distances from grid distances; state plane coordinates require a combined factor.
- Close traverses and compare closures to the project's accuracy standard.
Worked example
A 500-ft backsight checks 0.03 ft long. That could be prism constant, centering, or atmospheric error, not necessarily a bad monument. Recheck the instrument setup and prism constant, then repeat the observation. If the boundary corner is an original monument, do not move it to make the shot 'close.'
Traps
Accepting a single GNSS shot; mixing grid and ground coordinates; ignoring temperature and pressure; and recording a monument as 'found' without describing its condition.