Field Track - Level II Work Elements
The Field track at Level II tests whether you can carry routine field work without supervision: set up and check an instrument, take observations that will close, run a level loop, store a defensible RTK position, and write notes the office can retrace.
Set-up and checks
Level the tribrach with its plate bubble, then verify the optical plummet puts the instrument over the mark. An electronic bubble does not replace the plate bubble. Log instrument and prism serial numbers; an unrecorded swap invalidates the loop.
Angles
Observe both faces at control stations. Averaging direct and reverse cancels collimation error, and the departure of reverse from direct + 180° measures it. Close the horizon at each station: the angles around the point must sum to 360°.
Leveling
Keep backsight and foresight distances equal; that cancels collimation error and most curvature and refraction (combined, about 0.0206 ft per thousand feet, squared). Set turning points on solid ground, keep the rod plumb, and close every loop on a known benchmark.
GNSS
Use a verified antenna height, check PDOP and mask angle (commonly 10–15°), confirm a fixed solution before storing, and repeat the observation at a different epoch. A check shot on a known point catches base-coordinate blunders.
Field notes
Permanent ink, no erasures: strike through with one line and initial. Record date, weather, party, equipment, and a sketch.
Worked example. A direction reads 145°12'18" direct and 325°12'24" reverse. Reverse minus 180° equals 145°12'24", which is 6" from direct - a 3" collimation error. The correct direction is the mean, 145°12'21". Booking the direct face alone would import 6" into every angle turned from that setup.
Traps. Fitting the wrong prism constant; unequal backsight and foresight distances hiding a systematic error; assuming a fixed RTK shot is correct without a check; storing float positions as fixed; treating a side shot as a traverse station.