Measurement, Computations, and Field Procedures
Field measurement and error control
Exam questions in this domain test whether you can select equipment, design a field procedure, and evaluate the quality of the result. Know the difference between precision and accuracy, the behavior of random versus systematic error, and the need for redundant observations. A total station traverse should be closed or tied to control; angles and distances should be observed with appropriate field checks. GNSS work requires attention to datum, projection, initialization, and the difference between autonomous, differential, and RTK/network solutions. Do not confuse ellipsoid height with orthometric height.
Computations
Be comfortable with latitudes and departures, coordinate geometry, area by coordinates, curve elements, and traverse adjustment. A closure ratio is total linear misclosure divided by traverse perimeter, expressed as 1 part in N. A common trap is mixing units or using grid distances where ground distances were intended. State plane and other projected coordinates require scale and convergence awareness; a question may ask for a ground distance from grid coordinates and expect you to recognize the difference.
Worked example
A closed traverse has a perimeter of 5,000.00 ft and a linear misclosure of 0.25 ft. Closure ratio = 5,000 / 0.25 = 20,000, so the closure is 1:20,000. A candidate who reports 1:200,000 has inverted the ratio.
Rule of thumb
One second of arc subtends about 0.005 ft at 1,000 ft, about 0.025 ft at one mile, and about 101 ft of latitude on the Earth's surface. Use this to sanity-check angular misclosure and coordinate shifts.