Stonex R20 – User Manual 80
16. Appendix
16.1. Atmospheric Correction
The distance results measured by the instrument are correct only when corrected by the atmospheric correction
value of ppm (mm/km, 10
-6
). This scale correction value is calculated from the local meteorological parameters
entered at the time of measurement. The atmospheric correction is related to factors such as atmospheric pressure
and temperature.
For high precision distance measurements, the atmospheric correction must be accurate to 1ppm,the relevant
meteorological parameters must be re-determined at the time of the distance measurement. The air temperature
must be accurate to 1°C and the atmospheric pressure to 3hPa. The prevailing atmospheric parameters are entered
into the instrument and the atmospheric correction for the distance measurement is automatically calculated.
The instrument default parameters:
Air temperature 20 ℃
Atmospheric pressure 1013.25 hPa
Atmospheric correction 0 ppm
Atmospheric correction formula:
kPT = 279.097 - 0.29528 × P / (1 + 0.0036 × T)
kPT: atmospheric correction (ppm)
P: pressure (hPa)
T: temperature (℃)
SD = SD
0
× (1 + kPT)
SD
0
: original slope distance
SD: corrected slope distance
Atmospheric correction values can be conveniently found on the atmospheric correction chart below. The
temperature is read on the horizontal axis of the chart and the pressure on the vertical axis, the value on the diagonal
of its intersection is the atmospheric correction value.