[GRASS-dev] [GRASS GIS] #2229: error in projection definition

[GRASS GIS]

#2229: error in projection definition
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  Reporter:  vincent             |      Owner:  grass-dev@…
      Type:  defect              |     Status:  new
  Priority:  normal              |  Milestone:  7.0.5
 Component:  Projections/Datums  |    Version:  svn-releasebranch70
Resolution:                      |   Keywords:  pseudomercator
       CPU:  Unspecified         |   Platform:  Unspecified
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Comment (by mlennert):

 Replying to [comment:20 vincent]:
 > Replying to [comment:19 mlennert]:
 > > As discussed during the code sprint, the issue is because of the very
 weird nature of this "projection" system [...]
 > I fully agree with these comments
 > > The most reasonable conclusion, however, was to not use this system at
 all because of it's weird nature. Several official administrations forbid
 its use...
 > Ok bu sooner or later, users may have to manage data in this
 "projection" system, and they might be puzzled (angry) to see it does not
 work despite a proper location definition via the epsg code.
 > > In the discussions, one idea that came up was to provide alternative
 datum transformation parameters for this system, one on the sphere and one
 on the wgs84 ellipsoid.
 > If there is no solution to automatically "patch" this issue, meanwhile
 we could edit a wiki page describing a solution (like passing a proj.4
 chain) to the location's creation.
 >

 At this stage, I'm not sure what the solution would be. I created a
 location with the proj.4 chain you gave:


 {{{
 +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0
 +k=1.0 +units=m +nadgrids=@null +wktext  +no_defs <>
 }}}

 and then attempted to project a file from EPSG 31370 (Belgian Lambert
 1972) to that location, but I got the following error:


 {{{
 WARNING: pj_transform() a échoué: failed to load datum shift file
 ERROR: Unable to re-project vector map <rues at urbis> from <Belgique31370>
 }}}

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Ticket URL: <https://trac.osgeo.org/grass/ticket/2229#comment:21>
GRASS GIS <https://grass.osgeo.org>