[Dxspider-support] Reciprocal Heading Error

Rene Olsen rene_olsen at post3.tele.dk
Tue Oct 22 17:00:03 BST 2002

Hi Saul.

> Just thought I'd point out a problem you may or may not be aware of. The
> calculation of Reciprocal beam heading in sh/head (or anywhere else it's
> used) is not correct. I looked at the bdist function that does the deed
> and it looks like maybe there's a sign problem because you're
> calculating the reciprocal bearing by using the range and bearing
> function and just reversing the from and to coordinates. I didn't try to
> isolate the problem in the calculation but, wouldn't it be simpler to
> just calculate the reciprocal heading by just adding 180 degrees if the
> heading is less than 180 or subtracting 180 if heading is greater than
> or equal to 180? I don't know if you use the distance part of the
> reciprocal bearing/distance calculation, but the distance is the same as
> that calculated in the bearing/distance in the first place. If you need
> the distance returned in the reciprocal calculation, just use the same
> distance calculated for the bearing.

What the command sh/heading actually shows is the beam heading from you to X and 
from X to you. It does NOT show short path/long path. One I also thought that reciprocal 
heading would be long path. But in this case it is the heading from X to you, which 
sometimes gives some funny (but correct) numbers :-)

Vy 73 de Rene / OZ1LQH

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