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Subject: T & B Corrections
From: Chuck Taylor (ctaylor@XXX.XXX)
Date: Thu Nov 09 2000 - 18:01:06 EST
The T & B (Temperature & Barometric Pressure) corrections in the Nautical
Almanac are provided for occasions when temperature and barometric pressure
differ from the "standard" temperature of 10 degrees Celsius (50 degrees
Fahrenheit) and 1010 millibars (29.83 inches of mercury). They are applicable
mostly to low-altitude sights and allow for the fact that refraction can vary
with T & B.
An aeronautical engineer friend of mine tells me than "Standard Temperature and
Pressure" in his world are 15 degrees Celsius (59 degrees Fahrenheit) and 1013
millibars (29.92 inches of mercury).
Does anyone know the logic for selecting 10 degrees Celsius and 1010 millibars
as the basis for the refraction tables? There must be some historical reason,
but I can't find it in Bowditch.
Chuck Taylor
Everett, WA, USA
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