Work out total station distance correction instantly with clear inputs, formula shown and shareable results.
An electronic distance measurement is corrected in three steps: the atmospheric correction in parts per million for the prevailing temperature and pressure, the prism constant offset, and finally reduction to the horizontal by the cosine of the vertical angle. At 250 metres a 12 ppm error is only 3 mm, but on a two kilometre line it becomes 24 mm.
Corrected slope distance
Corrected = measured x (1 + ppm / 10^6) + prism constant
Reduction
Horizontal = corrected x cos(vertical angle); height difference = corrected x sin(vertical angle)
Corrected = measured x (1 + ppm / 10^6) + prism constant. An electronic distance measurement is corrected in three steps: the atmospheric correction in parts per million for the prevailing temperature and pressure, the prism constant offset, and finally reduction to the horizontal by the cosine of the vertical angle.
It is an offset, not a proportion, so it applies equally to every distance. Mixing a minus 30 mm prism with an instrument set for zero introduces a constant 30 mm error into every measurement.
This calculator takes 4 inputs: Measured slope distance, Vertical angle, Atmospheric correction, Prism constant. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.