•
Air temperature to 1 °C
•
Air pressure to 3 mbar
•
Relative humidity to 20 %
The air humidity influences the distance measurement if the climate is extremely hot and damp.
For high precision measurements, the relative humidity must be measured and entered along
with the air pressure and the temperature.
ppm
+5
+1
+2
+3
+4
+0
-10
-20
0 10 20 30 40 50
°C
100%
80%
60%
40%
20%
TS_104
ppm Air humidity correction [mm/km]
%
Relative humidity [%]
C°
Air temperature [°C]
Type
Index n
Carrier wave [nm]
Combined EDM
1.0002863
658
The index n is calculated from the formula of the IAG Resolutions (1999), and is valid for:
Air pressure p:
1013.25 mbar
Air temperature t:
12 °C
Relative air humidity h:
60 %
Formula for visible red laser
· 10
x
4.126 · 10
-4
· h
-
0.29535 · p
Δ
D
1
= 286.338 -
002419_002
D
D1
Atmospheric correction [ppm]
p
Air pressure [mbar]
t
Air temperature [°C]
h
Relative humidity [%]
a
1
273.15
x
(7.5 * t/(237.3 + t)) + 0.7857
If the basic value of 60 % relative humidity as used by the EDM is retained, the maximum possi-
ble error in the calculated atmospheric correction is 2 ppm, 2 mm/km.
Air humidity
Air humidity correction
Index n
Formulas
62
Technical Data