Sokkia SRX1, Operator'S Manual, Page: 130 / 184

21. CHANGING THE SETTINGS
122
・ The following are samples of the prism constant correction values of reflective prisms from
Sokkia.
Prism constants and aperture settings can be set for each prism. The prism constant and
aperture values displayed in the EDM tab will change to reflect the reflector type selected in
"Reflector".
●
ppm tab
• [0ppm] : Atmospheric correction factor returns to 0 and temperature and air pressure are set to
the factory settings.
• Atmospheric correction factor is calculated and set using the entered values of the temperature
and air pressure. Atmospheric correction factor can also be entered directly.
Items set, options, and input range (*: Factory setting)
Temperature: -30 to 60°C (15*)
Pressure: 500 to 1400hPa (1013*), 375 to 1050mmHg (760*)
Humidity: 0 to 100% (50*)
ppm (Atmospheric correction factor): -499 to 499 (0*)
•The "Humidity" item is displayed only when the "ppm setting" in "Obs. condition" is set to
"+Humidity".

Atmospheric correction factor
The SRX measures the distance with a beam of light, but the velocity of this light varies
according to the index of refraction of light in the atmosphere. This index of refraction varies
according to the temperature and air pressure.
• To precisely determine the atmospheric correction factor, the average temperature and air
pressure along the measurement beam route must be taken. Take care when calculating the
correction factor in mountainous terrain as the difference in height will result in differences in
atmospheric conditions between two points.
• The SRX is designed so that the correction factor is 0 ppm at an air pressure of 1013 hPa and
a temperature of 15°C.
AP01AR (Constant = 40mm)
Correction Value = -40
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