Leica TS13 - Page 76

If the basic value of 60 % relative humidity as used by the EDM is retained, the
maximum p
ossible error in the calculated atmospheric correction is 2 ppm,
2 mm/km.
The values for DD
2
ar
e always negative and are derived from the following for-
mula:
TS_106
ΔD
2
= -
H
R
· 10
6
DD
2
R
eduction to mean sea level [ppm]
H Height of EDM above sea level [m]
R
6.378 * 10
6
m
The magnitude of the projection distortion is in accordance with the projection
system used in a particular country, for which official tables are generally avail-
able. The following formula is valid for cylindrical projections such as that of
Gauss-Krüger:
T
S_107
ΔD
3
=
X
2
2R
2
· 10
6
DD
3
Projection distortion [ppm]
X Easting, distance from projection
zero line with the scale factor 1
[km]
R
6.378 * 10
6
m
In countries where the scale factor is not unity, this formula cannot be directly
ap
plied.
Atmospheric corrections in ppm with temperature [°C], air pressure [mb] and
heig
ht [m] at 60% relative humidity.
TS_108
-40
-35
-30
-25
-20
-15
-10
-5
0
5
10
15
20
25
30
35
40
45
50
55
60
65
70
75
80
85
90
95
100
105
110
115
120
125
130
135
140
50°C50°C
40°C40°C
30°C30°C
20°C20°C
10°C10°C
0°C 0°C
-10°C-10°C
-20°C-20°C
550 mb
5000 m 4500
600 650 700 750 800 850 900 950 1000 1050 mb
550 mb 600 650 700 750 800 850 900 950 1000 1050 mb
4000 3500 3000 2500 2000 1500 1000 500 0 m
Reduction to mean
sea level DD
2
Projection distortion
DD
3
Atmospheric
co
rrections °C
76 Technical Data