[GRASS-dev] [GRASS GIS] #2208: r.in.gdal/v.in.ogr: reprojection at import

[GRASS GIS]

#2208: r.in.gdal/v.in.ogr: reprojection at import
----------------------------------------+-----------------------------------
 Reporter:  mlennert                    |       Owner:  grass-dev@…              
     Type:  enhancement                 |      Status:  new                      
 Priority:  normal                      |   Milestone:  7.0.0                    
Component:  Default                     |     Version:  unspecified              
 Keywords:  projection import gdal ogr  |    Platform:  Unspecified              
      Cpu:  Unspecified                 |  
----------------------------------------+-----------------------------------

Comment(by mlennert):

 Replying to [comment:9 mmetz]:
 > Replying to [comment:8 mlennert]:
 > > Replying to [comment:6 mmetz]:
 > > > Replying to [comment:5 mmetz]:
 > > > > Replying to [comment:3 mlennert]:
 > > > > > Replying to [comment:2 mmetz]:
 > > > > > > Replying to [comment:1 martinl]:
 > > > > > > > reprojection option available for r.in.gdal/v.in.ogr would a
 step forward from user perspective.
 > > > > > >
 > > > > > > You would need to supply all options of [r|v].proj. Moreover,
 vector data might need preprocessing (adding vertices to lines/boundaries)
 in order to provide realistic and topologically correct results. The
 reprojection option could IMHO be best implemented in a script which calls
 r.in.gdal/v.in.ogr and then r.proj/(v.split + v.proj).
 > > > > > >
 > > > > >
 > > > > > I had actually thought that it might be possible to integrate
 GDAL/OGR library tools such as GDALWarpOperation and
 OGRCoordinateTransformation directly into r.in.gdal/v.in.ogr.
 > > > > >
 > > > > > But maybe you're right and we should not touch the general GRASS
 structure of import into one location + reproject into another, and rather
 use a wrapper.
 > > > >
 > > > > (Ongoing discussion on the dev-ml)
 > > > >
 > > > > My point for a wrapper script which calls r.in.gdal/v.in.ogr and
 then r.proj/v.proj is about reprojection pitfalls.
 > > >
 > > > I have created the addon script r.in.proj which imports and
 reprojects (if necessary) a GDAL datasource. It is by purpose educational,
 i.e. the user needs to specify the resampling method and by default the
 average target resolution is estimated, but the input is not reprojected.
 This forces the user to think about both the resampling method and a
 reasonable output resolution. If in doubt, read the manual...
 > >
 > > Great work, thanks a lot (including for the educational approach) !
 > >
 > > A few little bugs I've come upon:
 > >
 > > 1) 'output' is said to be =input by default but that does not seem to
 be the case anywhere in the source code, so output is a mandatory option.
 > >
 > > 2) There are some strings (n,s,e,w) that need to be converted to float
 for calculation in line [https://trac.osgeo.org/grass/browser/grass-
 addons/grass7/raster/r.in.proj/r.in.proj.py#L290 290].
 > >
 > > 3) The way I would understand the 'extents' option this should import
 the entire map. So this would entail that the region is adapted to the map
 prior to reprojection. The '-n' flag of r.proj does not do this, IIUC, so
 when I try to import I get an empty map. I guess this needs a first dry
 run of r.proj with the -g flag.
 >
 > Thanks for testing. All fixed in r64352.

 I still get an error:


 {{{
 Traceback (most recent call last):
   File
 "/data/home/mlennert/SRC/GRASS/grass_trunk/dist.x86_64
 -unknown-linux-gnu/scripts/r.in.proj", line 337, in <module>
     main()
   File
 "/data/home/mlennert/SRC/GRASS/grass_trunk/dist.x86_64
 -unknown-linux-gnu/scripts/r.in.proj", line 302, in main
     grass.message(_("Specified target resolution: %g") %
 outres)
 TypeError: float argument required, not str
 }}}

 I can solve this with


 {{{
 ===================================================================
 --- r.in.proj.py        (révision 64355)
 +++ r.in.proj.py        (copie de travail)
 @@ -231,7 +231,7 @@
      region = grass.region()

      if tgtres is not None:
 -        outres = tgtres
 +        outres = float(tgtres)
      else:
          outres = (region['ewres'] + region['nsres']) / 2.0

 }}}

 but don't know if that is your intention.

 Two more usability remarks:

 1. You actually run r.in.gdal (line 187) and you test afterwards, whether
 a projection system was recognized or an XY-location created. Could this
 test be put after line 160 by looking at 'insrs' ? This would avoid going
 through the import which can take a while if the dataset is heavy.

 2. When the '-i' flag is not set a short message at the end should inform
 the user about the fact that the layer has not been imported, especially
 since the module spits out a 'Raster map <XYZ> created' during the process
 (coming from the creation of the raster map in the temp loc) and that you
 have to dig into the doc to understand that you have to explicitly set the
 -i flag.

-- 
Ticket URL: <https://trac.osgeo.org/grass/ticket/2208#comment:11>
GRASS GIS <http://grass.osgeo.org>