Topcon GPT-3000 Series, Instruction Manual

Page: 134 / 180

12-1
12 SETTING ATMOSPHERIC CORRECTION
12 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.
12.1 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 Tempe20°C, Air pressure 847hPa, l =1000 m
+ 50
×
10
-6
(50 ppm)
L = 1000 (1+50
×
10
-6
) = 1000.050 m
12.2 Setting of Atmospheric Correction Value
●
How to Set Temperature and Pressure Value Directly
Measure the temperature and air pressure surrounding the instrument beforehand.
Example : Temperature: +26°C, Pressure:1017 hPa
Operating procedure Operation Display
1
Press the [F4] key to get the soft key page 2 in the
distance measurement mode or page 3 in the
coordinate measurement.
[F4]
2
Press the [F3](S/A) key to set Set Audio Mode
from distance or coordinate measurement mode.
[F3]
3
Press the [F3](T-P) key.
[F3]
4
Input Temp.value and Pressure value.*1)
Mode returns to Set Audio mode.
Enter Temp.
Enter Pres.
*1) Refer to Section 2.6 “How to Enter Alphanumeric characters”.
●
Range : Temp. –30 to +60°C (0.1°C step) or –22 to +140°F (0.1°F step)
Pres. 560 to 1066.0hPa (0.1hPa step) ,420 to 800mmHg (0.1mmHg step) or
16.5 to 31.5inHg (0.1inHg step)
Ka : Atmospheric correction value
P : Ambient atmospheric pressure (hPa)
t
: Ambient Atmospheric temperature (°C)
Ka
279.85
79.585
P
×
273.15 t +
-------------------------- –
 
 
 
10
6 –
×
=
Ka
279.85
79.585 847
×
273.15 20 +
------------------------------- –
 
 
 
10
6 –
×
=
HR: 120°30'40"
HD* 123.456 m
VD: 5.678 m
MEAS MODE NP/P P1
↓
OFSET S.O S/A P2
↓
PSM:0.0 PPM 0.0
NPM:0.0
SIGNAL:[
❙ ❙ ❙ ❙ ❙
]
PRISM PPM T-P –––
TEMP. & PRES. SET
TEMP.
→
15.0 °C
PRES. : 1013.2 hPa
INPUT ––– ––– ENTER
TEMP. & PRES. SET
TEMP. : 26.0 °C
PRES. : 1017.0 hPa
INPUT ––– ––– ENTER