[Xastir] xastir/gpsd - losing it in gps.c

[Gerry Creager n5jxs]

The Fix Quality parameter, if I recall correctly, is
0 == Invalid
1 == Valid 2D
2 == Valid 3D
3 == Valid 3D/Augmented

Gerry

Curt, WE7U wrote:
> On Wed, 18 May 2005, Richard Polivka wrote:
> 
> 
>>I resorted to the old, old trick of inserting prints
>>into the code to track progress. In working with the
>>GPGGA section in gps.c, I found that the following
>>sentence fails parsing:
>>$GPGGA,115219,4301.1477,N,8803.0382,W,3,06,1.80,237.2,M,-34.460,M,,*77.
> 
> 
> This is what I have listed for GPGGA:
> 
> GPGGA,hhmmss,ddmm.mmm[m],{N|S},dddmm.mmm[m],{E|W},{0|1|2},nsat,hdop,mmm.m,M,mm.m,M,,[*CHK]
> 
> 
> Comparing the two, I see that the longitude is missing a digit, the
> number after the E/W is a 3, whereas I have listed only 0-2 as
> possible.  In the decode_gps_gga() function we specifically check
> for 1 or 2 for a GPS fix quality.  Perhaps the WAAS changes to the
> GPS's are where the '3' comes from and we should accept that?  That
> one's new to me.  Since I don't have any WAAS-enabled GPS'es I
> haven't seen that one.
> 
> W.r.t. the longitude string, I think we're handling that ok at
> present.
> 
> I'm tweaking the GPGGA parsing to allow a '3' for the fix quality.
> I'd like to know if that means a good fix and whether other numbers
> are possible.  I'll check that into CVS shortly.
> 
> The decode_gps_rmc() function doesn't have a similar problem as the
> fix quality is just 'A' or 'V' there.
> 
> I did see what might be other problems that we might come across
> later, w.r.t. looking for a '.' character in the lat/long strings
> during validation.  This could certaily cause problems for us later
> if GPS'es send strings of varying length for some of these fields.
> Everything I've seen to date just changes the number of digits after
> the decimal point, the digits before the decimal point are always
> zero-filled.
> 
> --
> Curt, WE7U.   APRS Client Comparisons: http://www.eskimo.com/~archer
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-- 
Gerry Creager -- gerry.creager at tamu.edu
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