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Subject: Re: Q: how to calculate refraction at higher altitudes on land?
From: Dov Kruger (dkruger@XXX.XXX)
Date: Thu Feb 28 2002 - 10:40:46 EST
Oops!
Dan,
At high angles (above 45 or so) you will have so little refraction in
the first place that any reduction in it won't make a significant
difference with what I originally said. You can just do your atmospheric
correction and that's more than it deserves. But at the lower angles,
the normal correction for pressure will presumably be too great, because
the reason the pressure is low is that you are high, not because your
whole region is experiencing low pressure.
In the worst case, consider you are looking down at the horizon. Near
the horizon, your line of sight is passing through sea-level air.
Halfway, it is passing through air at half your altitude. Since the
correction is small in any case, why not just try to divide it in half
and use that? You know the upper bound (no pressure correction) and the
lower bound (full pressure correction) so you know exactly how bad your
assumption can be.
Why not send us the raw data when you do it so we can take a look?
cheers,
Dov
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