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9 SETTING ATMOSPHERIC CORRECTION
9 SETTING ATMOSPHERIC CORRECTION
The velocity of light through air is not constant and depends on the atmospheric temperature and
pressure. The atmospheric correction system of this instrument corrects automatically when the
correction value is set. 15
°
C/59
°
F, and 1013.25hPa / 760mmHg / 29.9 inHg is as a standard value for
0ppm in this instrument. The values are kept in the memory even after power is OFF.
9.1 Calculation of Atmospheric Correction
The followings are the correction formulas. Unit; meter
The distance L (m) after atmospheric correction is obtained as follow.
L = l (1+Ka)
l :Measured distance when atmospheric
correction is not set.
Example : In case Temperature +20°C, Air pressure 847hPa, l =1000 m
+
50
×
10
-6
(50 ppm)
L
= 1000 (1+50
×
10
-6
) = 1000.050 m
Ka: Atmospheric correction value
P : Ambient atmospheric pressure (hPa)
t : Ambient Atmospheric temperature (°C)
Ka
P
×
t
+
-------------------------------–
–
×
=
Ka
×
+
----------------------------------------–
–
×
=
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