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a. Loop Traverse
Figure I-5 |
Previously computed unadjusted latitudes and departures are:
Line | Bearing | Length (ft) | Lat (ft) | Dep (ft) |
AB | S 68°05'35"W | 472.68 | -176.357 | -438.548 |
BC | N 19°46'00"W | 216.13 | +203.395 | -73.093 |
CD | N 45°55'20"E | 276.52 | +192.357 | +198.651 |
DA | S 54°59'15"E | 382.24 | -219.312 | +313.065 |
sum: |
1347.57 | +0.083 | +0.075 |
(1) Compute preliminary coordinates from the raw latitudes and departures:
(2) Determine latitude and departure closure errors:
Lat err = N_{A'} - N_{A} = 500.083' - 500.000' = +0.083'
Dep err = E_{A'} - E_{A} = 2000.075' - 2000.000' = +0.075'
Note that these match the latitude and departure column sums above.
(3) Compute and apply corrections to the coordinates using the Compass Rule, Equation (I-3).
Line AB
Because point A is a control point, its coordinates are not modified. The corrections are applied to the line's endpoint, point B.
Line BC
Remember to include the corrections for the previous line.
Line CD
Line DA
The corrected preliminary coordinates match the beginning coordinates of point A.
These coordinates also match those computed in the Coordinates section.