Measurement and Computation (Field Procedures)
Core concepts
Expect questions on total station and GNSS field procedures, angular closure, traverse adjustment (compass rule and transit rule), and coordinate geometry. Know how to compute latitudes and departures, misclosure, and precision ratios (e.g., 1:10,000). Understand error sources: instrument centering, target centering, refraction, and prism constant. Know the difference between random and systematic error and how each behaves in a traverse.
Traps
Questions often ask for the precision ratio but give closure in feet and total traverse length in chains-unit conversion is the trap. Another trap is confusing the compass rule (distributes error proportional to line length) with the transit rule (proportional to latitude/departure magnitude). Also watch for sign errors in latitudes/departures and for using the wrong formula for area (shoelace vs. trapezoidal).
Rule of thumb
Precision = total misclosure / total traverse length, expressed as 1:N. Always convert to consistent units before dividing.
Worked example
A traverse closes with misclosure 0.15 ft over 3,000 ft. Precision = 0.15/3,000 = 1/20,000, reported as 1:20,000. If the closure had been 0.15 ft over 1,500 ft, precision would be 1:10,000-half as precise.