Three benchmarks and an interior junction point are connected by six level lines forming three independent loops. Adjust the net by inspection, distributing each loop misclosure by line length and iterating until every loop closes.
Analyze· about 35 minutes by hand· 6 steps
Given
Three benchmarks A, B and C and an interior junction point J, connected by six level lines. Elevations are in US survey feet and are carried to 0.001 ft.
Observed elevation differences and line lengths: A to B, +4.512 ft, 1.6 miles; B to C, -9.874 ft, 2.0 miles; C to A, +5.340 ft, 1.8 miles; A to J, +2.061 ft, 1.0 mile; B to J, -2.462 ft, 1.2 miles; C to J, +7.400 ft, 1.4 miles.
Elevation of BM A is held fixed at 4,182.615 ft. B, C and J are all to be determined.
The three independent loops are taken as Loop I (A to B to J to A), Loop II (B to C to J to B) and Loop III (C to A to J to C).
Required
The misclosure of each of the three loops.
A correction to each of the six lines that closes all three loops simultaneously.
Adjusted elevations of B, C and J.
Work it through yourself before reading on - the solution below shows every step, so there is no way to skim it without giving the answer away.
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