[Xastir] MultiLine Footprint ISS Object

[Tom Russo]

On Wed, Oct 12, 2011 at 11:28:59PM -0600, we recorded a bogon-computron collision of the <russo at bogodyn.org> flavor, containing:
> On Thu, Oct 13, 2011 at 01:26:00AM -0400, we recorded a bogon-computron collision of the <ldeffenb at homeside.to> flavor, containing:
> > If the o/ISS doesn't get it (I've had mixed luck with non-9-character 
> > object names, maybe o/ISS*?), try a b/KJ4ERJ-15 which is the source of 
> > the object.  They're going out every 2 minutes, but you won't see them 
> > at aprs.fi as Hessu seems to be having some sort of backlog issue with 
> > his Raw packet display.
> 
> I'm using a connection to rotate.aprs.net port 14580.  Just switched the 
> filter to b/KJ4ERJ-15.  Will let you know.
> 

There we go, I just started getting the ISS objects.  Sad to say, none of the 
multiline data showed up on screen.

Station Info showing first two reports states:

Comment 10/12 23:33 :  }k1juNr`jn^wQzEw9q0g)['N)A059+E%Q"^%j.r<uN{
Comment 10/12 23:31 :  }k1‚PNPOOOOPN"N!MPLOLNLNLNLMMLNLNLOLOMPMPN{


which looks like the sequence got stripped off (comment should start with
" }" and end with "{sssss" where sssss is a sequence number.

But incoming data window for third report shows:
 1:NET-> KJ4ERJ-15>APZTLE,TCPIP*,qAC,KJ4ERJ-5:;ISS      *053518h3212.78N\14902.73WS }k1krNpahp\xPzEw:p1f+Z*N+B16:,E%P"\$h,p;rN{!wug!

which looks right at first blush.   But...

According to the spec, object comments can only be 43 characters long, and
if you strip off the " }k1k" that describe the line type, color, and scale,
and the "{sssss" characters for sequence, that leaves only 32, enough for
16 lat/lon pairs.  Your strings have 38 chars (19 lat/lon pairs) there.

>From the comments in Xastir's "make_multiline" function:
    // the APRS spec requires a max of 43 chars in the comment section of 
    // objects, which leaves room for only so many vertices in a multiline 
    //   number allowed= (43-(6-5))/2=16
    // 43chars - 6 for the sequence number- 5 for the starting pattern leaves
    // 32 characters for lat/lon pairs, or 16 pairs

I think Xastir is truncating the last 6 characters of the object comment,
which means it loses the sequence number --- and if it doesn't find one it
won't recognize the comment as multiline data.

Looking through the code I see multiple references to the 43 char limit for
object comments.  Those comments were probably written by Curt (and when I 
wrote make_multiline, I consulted the spec to assure I only accepted input 
lat/lon lists that would not exceed that limit).

Try sending out your footprints with only 16 vertices instead of 18, and lemme
know when to look for 'em.  I'll send you a screen shot as soon as I see
multiline data plotted.


-- 
Tom Russo    KM5VY   SAR502   DM64ux          http://www.swcp.com/~russo/
Tijeras, NM  QRPL#1592 K2#398  SOC#236        http://kevan.org/brain.cgi?DDTNM
 "One man alone can be pretty dumb sometimes, but for real bona fide
 stupidity, there ain't nothin' can beat teamwork." - Edward Abbey