[aprssig] antenna pointing based on ARS position report?

Scott Miller scott at opentrac.org
Wed Mar 26 20:20:20 EDT 2008

I know there are Az-El varieties out there.  Elevation's going to take 
some more calculation.  I think I can disregard the Earth's curvature, 
though - at 200 miles it should be what, about 130 feet?  Not enough to 
worry about when pointing an antenna.

So let's see.. elevation angle should be a = 
arctangent(height/distance), right?  I've already written an efficient 
atan(y/x) function, so I can reuse that.  I guess the only additional 
computation would be getting height and distance into the same units. 
That shouldn't take TOO much code space.

I think I'll just start with azimuth, though, if someone can give me the 
proper format, and has the hardware to try it out and let me know if it 


Jason KG4WSV wrote:
> On Wed, Mar 26, 2008 at 6:56 PM, Scott Miller <scott at opentrac.org> wrote:
>> I started working on that for the T2.
> Cool.  I don't know much about rotor controllers, so not sure about a
> standard format. I just thought it would be nice for an automated
> ground station for ATV balloons.  I think I've seen stuff for
> satellite tracking (maybe in conjunction with predict?) but balloons
> are quite a different animal.
> Are rotors generally azimuth only, or are there az-el varieties
> available?  Depending on the time of year, the elevation from the
> launch site to the balloon can be 90 degrees.
> -Jason
> kg4wsv
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