This code of practice provides guidelines for the use of Electronic Distance Measuring (EDM) instruments in surveying. It details the operating principles, sources of error, field procedures for accurate measurement, and the methodology for calibration and applying atmospheric corrections.
Lays down general requirements and methods of test for electronic distance measuring instruments used in surveying.
Quick Reference Values
Standard temperature for calibration20 °C
Standard pressure for calibration760 mm Hg
Standard relative humidity for calibration60%
Typical accuracy of short-range EDM±(3mm + 2ppm)
Typical wavelength for infrared EDM0.8 to 0.95 μm
Key Formulas
First Velocity Correction (ppm) = (279.6 - 0.925t - 2.24P) + 0.05e — Simplified formula for atmospheric correction
Practical Notes
Atmospheric corrections for temperature and pressure are critical for achieving specified accuracy; never use default or assumed values for high-precision work.
Always verify the prism constant setting in the instrument matches the actual constant of the reflector being used, as mismatches are a common source of systematic error.
Regular field checks, such as measuring a known baseline, are essential to monitor instrument performance between formal calibrations.