[GRASS5] GPS connectivity

Rich Shepard rshepard at appl-ecosys.com
Wed May 24 18:40:15 EDT 2000

On Wed, 24 May 2000, Andreas Lange wrote:

> http://mitglied.tripod.de/AndreasLange/grass/gps.html

  Ah! This works, thank you.
> I don not plan to deal with differential correction, i think that users
> that can afford and need dgps accuracy should go with commercial
> software. They should contact their vendor for unix/linux software. If
> the receiver uses NMEA-sentences or the binary format is documented
> postprocessing should be possible in theory on linux/unix. But this
> exceeds my resources and time. 

  I won't bore you with my long dialog with Corvallis Microtechnology, Inc.
They keep telling me that they can find only about 8 of us who want to use
their software on linux. And, they're adding more and more GIS features to
their software. Doesn't matter that many of us don't need it. They sell the
package for a large amount of money, and won't go to using GRASS because
they can't sell it as a proprietary product. Trying to convince them that
there is another model for making money with open source software falls on
deaf ears. I'm giving up.
> There are already many libraries/programs for up- and downloading data
> to gps receivers, _but_ they all have several drawbacks: They are
> model-specific (mostly garmin), as the protocols are vendor specific. 

  With CMT, everything is proprietary. I doubt that I could figure out how
to do the mission planning and job transfer to/from the handheld computer
via linux-based software. Also, the differential correction requires their
software that talks to their data structures. Sigh. That's how the keep the
prices so high.

  My GPS system is high precision (just below surveyor grade). I need this
for the 60-90 cm vertical accuracy so I can build DEMs of mine sites. Almost
no suitable elevation data exist. When it does, it's too coarse (say 15 m
contours) or too old, so I have to generate my own. Of course, the 30 cm
horizontal accuracy is far greater than biological reality, but that degree
of accuracy does help when orthorectifying aerial photos.
> For us european users additional problems arise: 
> I need map datum conversion as the german topo maps are in potsdam 1950
> datum, which is not supported by most receivers. With SA turned off the
> map datum shift that was used with GRASS is not sufficient (~30 m
> accurate). Further i need projecting/inverse projecting. All this should
> be done with no or little user input, which needs some programming (on
> the GRASS GIS side!).

  My CMT systems permit data collection in only three coordinate systems:
lon/lat, UTM and State Plane Coordinates. I don't think there's an option to
use anything else.

Dr. Richard B. Shepard, President

                       Applied Ecosystem Services, Inc. (TM)
              Making environmentally-responsible mining happen. (SM)         
            2404 SW 22nd Street | Troutdale, OR 97060-1247 | U.S.A.
 + 1 503-667-4517 (voice) | + 1 503-667-8863 (fax) | rshepard at appl-ecosys.com

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