[DebianGIS-dev] Bug#456149: gpsdrive: Doesn't display my altitude

[Andreas Putzo]

On Dec 17  21:18, Andrew McMillan wrote:
> On Mon, 2007-12-17 at 00:10 +0100, Andreas Putzo wrote:
> > On Dec 14  20:19, Andrew McMillan wrote:
> > > > > GPSDrive is not displaying any altitude reading from my GPS (a Garmin
> > > > > 60CSx).  If I telnet to the gpsd port on my local machine I definitely
> > > > > do see my altitude coming through on the various data streams available.
> > >
> > > The GPS itself is a Garmin GPSMap 60 CSx which has a barometric
> > > altimeter, can see 10 satellites at the time and is itself displaying
> > > altitude and '3D' in it's own status.
> > > 
> > > Here is a sample from connecting to gpsd now.
> > 
> > There are no GSA sentences in your sample log and i think gpsdrive
> > heavily relies on them to determine whether it knows the altitude or
> > not.
> > According to the manual of the 60CSx the device should use GSA. 
> > Did you set the Serial Data Format in the Interface Setup menu to NMEA
> > and if not, can you please verify if the problem persists with this
> > setting?
> 
> I can set the serial data format to 'NMEA', but it doesn't make a
> difference because I'm using the USB connection.  It looks like the
> Garmin will only output in the 'Garmin' format via the USB connection,
> so gpsdrive is depending on the 'on the fly' translation done by gpsd
> for non-NMEA units.
> 
> On the other hand, gpsd is certainly *providing* the altitude within the
> NMEA output, viz:
> 
> $GPGGA,055148,4106.5421,S,17452.2917,E,1,09,,94.9,M,16.836,M,,*42

> It looks like the GSA sentence is not produced by gpsd when it's doing
> it's on-the-fly translation. It does provide a 'q' command which returns
> essentially the same data, so it could probably be added.
> 
> On the other hand, perhaps using the GSA message as the sole source of
> altitude data seems short-sighted, especially if there are GPS out there
> which can provide greater altitude accuracy by combining the GPS data
> with other sensors internally.
> 
> I've filed bug #456634 against gpsd asking if it can also provide GSA
> sentences when synthesizing NMEA output, but I think it would still be
> nice if gpsdrive were capable of using the GGA output as an alternative
> as well.

IMHO gpsdrive shouldn't try to parse raw gps data itself altogether :)
There was a DBUS interface to gpsd which should work with garmin
but it is currently broken. 
Anyway, i will talk with upstream about this. 


Regards,
Andreas