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[aprssig] Satellite positions: Objects or Stations?

Heikki Hannikainen hessu at hes.iki.fi
Sat Oct 15 17:06:48 UTC 2011


On Sat, 15 Oct 2011, Bob Bruninga  wrote:

> In your generated ISS Position from the ISS callsign, of course, you 
> will have to add a note on he end in the comment field to the effect "de 
> KJ4ERJ" of course.

I have to say that I would greatly prefer to see ISS as an object, not a 
station. There is a standard way to transmit a position of something on 
behalf of that something, and still indicate the source of the 
transmissions, and that's objects (and items). If it would be a station, 
I, as an user, would be assuming the transmissions are actually 
transmitted by the real ISS instead of Lynn's software. My software would 
naturally make the same assumption and make it's user have the same 
belief.

The "de KJ4ERJ" would be non-standard and non-parseable since it would be 
in the free-form comment text field.

I also have to admit I'm also not a big fan of transmitting satellite 
tracks on the APRS-IS, since they can't be transmitted very often (to not 
flood the APRS RF channel and the IS), and the satellites move very fast - 
the distance between the transmitted positions is so large that the APRS 
user will rarely see them in his rather zoomed-in local view, unless it 
happens to go right overhead and the transmission happens on the exact 
right moment, or unless the user will specifically look up the station 
using his client software (in which case he could use software which 
calculates the position from the keplers as well). I honestly believe it 
might make more sense to regularly transmit the keplers instead and 
implement the position calculation on the client side.

For example, even in Helsinki, on the south coast of Finland, ISS 
would never cross the area filters for transmitting igates, or the APRS-IS 
clients displaying traffic in Finland, although ISS can be regularly 
worked from here.

The message server replying with the next pass information, on the other 
hand, is very useful indeed! Thank you!

   - Hessu




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