[aprssig] ISS Tracking & Pass Information SPEEDS

Bob Bruninga bruninga at usna.edu
Sat Oct 15 11:24:48 CDT 2011

I konw you have read all the specs and errata better han just about anyone, so I doubt we can find it.  But it was a proposal to account for things greater than 999 knots.  ANywayy, use 999 for satelites, its the best we can do.


>Can you point me to some definition or documentation of that?  I don't
>recall having read that anywhere in all of the specs I've read.
>Certainly my dead reckoning code doesn't take that into account!
>Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32
>On 10/15/2011 9:05 AM, Bob Bruninga wrote:
>>> Wait, how is the radio going to know the
>>> direction the satellite is moving from a
>>> single courtesy posit?
>> Yes, you put in 999 in the speed field.  Way back in 1996 or so we defined special speeds for very fast things.  I think 999 means orbital speed 17,500 MPH, 998 is the speed of sound etc.  But it doesnt matter.  It just gives something that the display software can use to draw the speed and direction vector.
>> Bob, Wb4APR
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