[GRASSLIST:971] Re: live GRASS/GPS interface

[Hamish]

> > I've been thinking about how to do a real-time GRASS/GPS interface.
> >
> > General idea is to have a GPS feeding NMEA statements into the
> > laptop's serial port, and have a program running in the background
> > which parses the statement, feeds it through PROJ, and appends the
> > result into a site_lists/gps_track file, as well as replacing the
> > single point in a site_lists/latest_postion sites file. Lat-Lon,
> > Time, COG, SOG, other GPS messages would be written to the site's
> > comments. (or even run r.what for that position and use that in the
> > comment string)
> > ...
> > Not very clean, but I think it should work.
> ...
> I think that what you described (write to site files + d.sites etc.)
> can be easily done in few minutes but it is far from optimal solution.

It took me more than a few minutes, and yes, it is a far from optimal
solution, but hey, it works! It's just a quick proof of concept bash
script and should be rewritten in C using the GRASS projection & sites
libraries once I figure them out. Feel free to give it a try:

http://bambi.otago.ac.nz/hamish/m.realtime_gps.sh

While it should work with any GPS or LORAN C system that can send NMEA
sentences to the serial port, I tested it out with a Garmin 48 handheld.
You'll need to modify the USER_PROJ= line at the top for your particular
dataset, and set the sample frequency as needed (currently 30 seconds).
The "current location" marker will show a time-stamp, and other text such
as underlying raster map values can be displayed as well (currently GPS
altitude).
Needs gpsd, netcat, and cs2cs. (see comments in the script)


> I would suggest PostGIS as data store (as ready for use solution for
> simultaneous read/write access) and QGIS as interface.
> It would require some simple extension for vector layer in QGIS
> (periodically zoom to vector). QGIS can work with both PostGIS
> and GRASS data. GRASS can also access PostGIS data.

Two thoughts --

As the present sites format is due for retirement, PostGIS or GRASS
5.1(5.7) vector-points format is the preferable long term solution.

On the other hand, I'd think this would be quite useful tool for the
handheld-PDA GRASS people, offering a bit more power than pyGPS does
currently. Has anyone gotten PostGIS or GRASS 5.1(5.7) with its database
needs working on a handheld? Is this an issue? Does QGIS run on
handhelds yet? Does this script+QGIS offer anything over pyGPS?


regards,
Hamish