11 setting atmospheric correction, 1 calculation of atmospheric correction, 2 setting of atmospheric correction value – Topcon GTS-823A User Manual
Page 117: 11 setting atmospheric correction -1, Chapter 11 “setting atmospheric correction”, f, See chapter 11 “setting, Atmospheric correction
11-1
11 SETTING ATMOSPHERIC CORRECTION
11
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.
l
Setting the atmospheric correction value is in the STAR key (
H
) mode.
11.1 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
11.2 Setting of Atmospheric Correction Value
l
How to Set Temperature and Pressure Value Directly
Measure the temperature and air pressure surrounding the instrument beforehand.
Example : Temperature: +26°C, Pressure:1020 hPa
Operating procedure
Operation
Display
1
Press STAR (
H
) key.
Press the [F6] key twice to get the page three.
[
H
]
[F6] twice
2
Press the [F2] key.
Current setting value is displayed.
[F2]
3
Input Temp.value and press [ENT] key.
[Example] Temp. : +26
°
C
The cursor moves to Pressure setting
automatically
Enter
value
[ENT]
4
Input Pressure value, and press [ENT].
[Example] Pres. :1020.0hPa.
The display returns previous mode.
*1) *2)
Enter
value
[ENT]
Ka
: Atmospheric correction value
P
: Ambient atmospheric pressure (hPa)
t
: Ambient Atmospheric temperature (°C)
Ka
279.67
79.535
P
×
273.15
t
+
--------------------------
–
10
6
–
×
=
Ka
279.67
79.535
847
Ч
273.15
20
+
-------------------------------
–
10
6
–
Ч
=
2003-10-10 14:30:40
3
↓
20.0
°
C
5.1ppm
-2.0 mm
1012.0hPa
Temperature setting
26.0
°
C
5.1ppm
-2.0 mm
1012.0hPa
Pressure setting
26.0
°
C
5.1ppm
-2.0 mm
1020.0hPa