TPC 2026 - Benchmarks

Benchmarks

Benchmarks are points of known elevation. When you take a shot on a benchmark, the elevation of the benchmark along with the target height, slope distance and vertical angle is used to establish the elevation of the instrument’s optics.

In TPC, each occupied point in a traverse, can have one tie to a benchmark. A benchmark does not require a horizontal angle or bearing tie.

Starting with an Assumed Benchmark Elevation

If you do not know the elevation of a benchmark, but you are sure it is a known benchmark with a known elevation, you can always assume an elevation, then enter the correct elevation at a later time and choose Tools | Recompute.

•If the benchmark point already exists, recall it into the Traverse View. If not, create a new point and enter the benchmark elevation.

•Choose Point Type | Benchmark.

•Enter the slope distance, vertical angle and target height of the shot to the benchmark. The elevation of the instrument optics is computed and stored internally.

If you have used an assumed elevation for more than one benchmark, you will need to enter the correct elevation for each benchmark used, then choose Tools | Recompute.

Translating an Assumed Benchmark Elevation

If you enter a Benchmark Traverse Point Sequence, like the one shown below, and use just a single benchmark with an assumed elevation, you can translate the entire traverse so that the benchmark ends up at the correct elevation.

This is an alternate to the 1) edit benchmark elevations then 2) choose Tools | Recompute. used above.

Benchmark Instrument Height (HI)

The HI for the benchmark point displays the elevation difference between the optics elevation and the elevation of the control point. If the control point elevation and the benchmark elevation are on the same grid, the HI should be close to the measured HI.

Benchmark Traverse Point Sequence

Note: The only restriction is that the benchmark point must immediately follow the occupied point or backsight point and cannot follow a sideshot.

Here is a typical terrestrial traverse sequence with benchmarks.

Point Type        Measured Data
1     OP
                   any distances or angles measured to the BS
2     BS
                   shot to BM, including HT (height of target)
99    BM          HI displays the difference between the elevation of the optics computed from the BM and the elevation of the OP, point 1