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Re: manual keplerian calculations



On Mon, 13 Oct 2008 19:04:13 +0100
Gordon JC Pearce MM3YEQ <gordonjcp@gjcp.net> wrote:
> cathrynham wrote:
> > Simon (HB9DRV) wrote:
> >> ----- Original Message ----- 
> >> From: "Jeff Wandling W7BRS" <jw@w7brs.com>
> >>   
> >>> ps. Again, reply directly -- this sort of question can make
> >>> enough spam on the DL to last you through Festivus.
> >>>
> >>>     
> >> A very good starting point is Dr Kelso's work on
> >> http://celestrak.com/
> >>
> >> And there's plenty (!) of C++ code out there which implements the 
> >> algorithms, so (worst case) you could figure things from the code.
> >>   
> > 
> > Bit of a digression, but you know what we need, one of these days,
> > is an open source code library for satellite tracking -- ideally
> > cross-platform for both *nix/Windows.  This is something that
> > would get use outside of the amateur community.
> > 
> 
> What does gpredict use?  It seems to work, so it would be a good
> start. I wish I knew more about how to calculate the predictions...

Gpredict uses sgp4/sdp4 C-code by 5B4AZ, see
http://5b4az.chronos.org.uk/pages/norad.html , which is a
translation of Kelso's pascal code into ANSI C. I have made certain
modifications and optimisations to improve efficiency when tracking a
large number of satellites simultaneously but the algorithms are the
same. For gpredict it is built and linked as a static library but it
is only a matter of linker options to build a shared library (the
windows version does indeed use DLL). The code itself is re-entrant.

I have also seen C++ implementations, which might be more suitable for
C++ applications. I believe the tracking code from Ham Radio Deluxe is
also available as GPL; don't know about its portability though.

73
Alex OZ9AEC
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