|
|
|
|
|||||
|
||||||
From: Marcel E. Tschudin (no email)
Date: Mon Aug 08 2005 - 13:28:02 EDT
Clive wrote
The following is one I use,
Ref = Tan (90-Altitude - 0.999139 * Altitude - (7.31 / (Altitude + 4.4)))
between -20 < Air Temp < +40, and 970 <air pressure mbs < 1050
or else use the correction below for abnormal temperature and Pressure
Abn = (( Baro Pressure - 80 ) / 930) * (1 / ( 1 + 0.00008 * (Refraction + 39) * (Temperature - 10))),
using mbs,deg celsius and deg Altitude.
Refraction = Ref * Abn and True Altitude = Observed Altitude - Refraction
Does anyone of you know where this correction for abnormal condition comes from?
What is actually ment with "abnormal"? As an example, the standard atmosphere also has temperatures below -20°C and air pressures below 970 mBar above a certain height, but this I would consider rather "normal". Could it be that the abnormal conditions refer to sea level conditions?
Thanks Marcel
|