Sokkia 30R Series Operator's Manual page 176

30. EXPLANATION
• Calculation of atmospheric correction factor allowing for humidity
The humidity has little influence, particularly on short distance measurements.
The effect of humidity should be considered in cases where it is very hot and
humid and high precision measurements are to be performed over a particularly
long distance.
When taking humidity into consideration, enter the atmospheric correction
factor calculated using the following formula.
Atmospheric Correction Factor (ppm) =
282.59 –
e (water vapor pressure) can be calculated using the following formula.
--------- -
×
e = h
100
ew 6.11 10
=
t : Air temperature (°C)
p : Pressure (hPa)
e : Water vapor pressure (hPa)
h : Relative humidity (%)
ew: Saturated water vapor pressure
168
×
0.2942 p
----------------------------------------- -
×
1 + 0.003661 t
ew
( × )
7.5 t
---------------------------
( )
t + 237.3
×
×
0.0416 e
+ ----------------------------------------- -
1 + 0.003661
×
t