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E
×
e
=
h
--------- -
100
E
=
6.11 10
With constant temperature, a pressure change of 3.6 hPa: an index change
of 1 ppm.
To perform high accuracy measurements, it is necessary to find the
atmospheric correction factor from even more accurate temperature and
pressure measurements and perform an atmospheric correction.
It is recommended that extremely precise instruments be used to monitor
the air temperature and pressure.
• Determine the temperature and pressure as follows.
Flat terrain
Mountainous terrain :Use the temperature and pressure at the
If it is not possible to measure the temperature and pressure at the midpoint,
take the temperature and pressure at the instrument station (A) and the
target station (B), then calculate the average value.
Average air temperature :(t1 + t2)/2
Average air pressure
• If the weather correction is not required, set the ppm value to 0.
(
×
)
7.5
t
--------------------------- -
(
)
t
+
237.3
×
:Use the temperature and pressure at the midpoint of
the line.
intermediate point (C).
:(p1 + p2)/2
259
33. CHANGING THE SETTINGS
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