Re: [Qgis-user] projection confused during import from Grass to QGIS
Hi Tyler, >From the gdalinfo output it would appear that you have no coordinate system defined for your layer(s). Note the Coordinate System line. Here you should--but do not--find datum, ellipsoid, projection type and its associated parameters, units of measure, etc. Since your data are not actually projected, you should see listed here something like: PROJCS["WGS84", GEOGCS["WGS84", DATUM["World Geodetic_Datum_1984", SPHEROID["WGS1984"], UNIT["degree"]], PROJECTION["Geographic"], PARAMETER["scale_factor",0.0], PARAMETER["false_easting",0.0], PARAMETER["false_northing",0.0] Your output lists only the affine coordinate geo-reference info (e.g., Origin, Pixel Size, Corners). With the addition of the negative signs in front of the (East/West) longitudes, as Randy pointed out, you get the correct E-W orientation, but you mention that a slight mis-alignment remains. About how much mis-alignment do you measure? Try setting the layer CRS explicitly in QGIS; I think that WGS84 is EPSG=4326. That might help. Too, if the mis-alignment is small (small is hard to define, I realize, when dealing with data in GPs), perhaps it has something to do with floating point round-off in GRASS (FCELL versus DCELL). Or, it could be related to the region, where the region set during export differed from that native to the layer(s) itself/themselves. These would account for only small differences. If there is larger mis-alignment (for instance two or more layers do not even overlap geographically), then something bigger is afoot. Keep us posted on progress. Paul On Tue, May 12, 2015 at 8:44 AM, Tyler Smith wrote: > On Mon, May 11, 2015, at 05:20 PM, Randal Hale wrote: > > > The header appears correct: > > > > > > tws:~$ head -6 tri_mean.asc > > > north: 46:53:04.633938N > > > south: 34:44:13.536462N > > > east: 68:50:28.1616W > > > west: 94:51:40.938811W > > > rows: 1458 > > > cols: 3122 > > > > > Shouldn't your east and west Lattitudes be negative? That would make it > > appear reversed as they stand now. At least I think - but I've not done > > what you are doing. > > I don't think so. The east and west lattitudes have a 'W' appended to > indicate west. Although I have tried manually deleting the W and adding > '-' in front of the digits. This does indeed flip the maps east to west, > but they are still somewhat misaligned with the actual projection. > > Regardless, I can export and import the layers to share them across > Grass installations without problem. The mis-projection only shows up > with gdal and QGis. > > Thanks, > > Tyler > > ___ > Qgis-user mailing list > Qgis-user@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/qgis-user > ___ Qgis-user mailing list Qgis-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-user
Re: [Qgis-user] projection confused during import from Grass to QGIS
On Mon, May 11, 2015, at 05:20 PM, Randal Hale wrote: > > The header appears correct: > > > > tws:~$ head -6 tri_mean.asc > > north: 46:53:04.633938N > > south: 34:44:13.536462N > > east: 68:50:28.1616W > > west: 94:51:40.938811W > > rows: 1458 > > cols: 3122 > > > Shouldn't your east and west Lattitudes be negative? That would make it > appear reversed as they stand now. At least I think - but I've not done > what you are doing. I don't think so. The east and west lattitudes have a 'W' appended to indicate west. Although I have tried manually deleting the W and adding '-' in front of the digits. This does indeed flip the maps east to west, but they are still somewhat misaligned with the actual projection. Regardless, I can export and import the layers to share them across Grass installations without problem. The mis-projection only shows up with gdal and QGis. Thanks, Tyler ___ Qgis-user mailing list Qgis-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-user
Re: [Qgis-user] projection confused during import from Grass to QGIS
Shouldn't your east and west Lattitudes be negative? That would make it appear reversed as they stand now. At least I think - but I've not done what you are doing. Randy Randal Hale North River Geographic Systems, Inc http://www.northrivergeographic.com 423.653.3611 rjh...@northrivergeographic.com twitter:rjhale http://about.me/rjhale http://www.northrivergeographic.com/introduction-to-quantum-gis On 05/11/2015 05:11 PM, Tyler Smith wrote: Hi, I'm exporting some data from Grass 6.4 to QGis as .asc files. The source location in Grass has the projection: g.proj -p -PROJ_INFO- name : Lat/Lon proj : ll datum : wgs84 ellps : wgs84 no_defs: defined -PROJ_UNITS unit : degree units : degrees meters : 1.0 I generated the asc file from Grass with: r.out.ascii input=tri_median@PERMANENT output=tri_median.asc When I import this into QGis, the layer is flipped east to west - the atlantic coast of NA appears on the west, rather than the east! The header appears correct: tws:~$ head -6 tri_mean.asc north: 46:53:04.633938N south: 34:44:13.536462N east: 68:50:28.1616W west: 94:51:40.938811W rows: 1458 cols: 3122 But gdal mis-reads it: tws:~$ gdalinfo tri_mean.asc Driver: GRASSASCIIGrid/GRASS ASCII Grid Files: tri_mean.asc Size is 3122, 1458 Coordinate System is `' Origin = (94.000,46.000) Pixel Size = (-0.008327994875080,-0.008230452674897) Corner Coordinates: Upper Left ( 94.000, 46.000) Lower Left ( 94.000, 34.000) Upper Right ( 68.000, 46.000) Lower Right ( 68.000, 34.000) Center ( 81.000, 40.000) Band 1 Block=3122x1 Type=Float32, ColorInterp=Undefined I also tried opening this map directly from Grass within QGIS using the Grass plugin. The problem persists - the projection of the map is flipped east to west when it appears in QGIS. Have I done something wrong somewhere, or is there a problem with the Grass 6.4 export or QGis/gdal import? Thanks! ___ Qgis-user mailing list Qgis-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-user
[Qgis-user] projection confused during import from Grass to QGIS
Hi, I'm exporting some data from Grass 6.4 to QGis as .asc files. The source location in Grass has the projection: g.proj -p -PROJ_INFO- name : Lat/Lon proj : ll datum : wgs84 ellps : wgs84 no_defs: defined -PROJ_UNITS unit : degree units : degrees meters : 1.0 I generated the asc file from Grass with: r.out.ascii input=tri_median@PERMANENT output=tri_median.asc When I import this into QGis, the layer is flipped east to west - the atlantic coast of NA appears on the west, rather than the east! The header appears correct: tws:~$ head -6 tri_mean.asc north: 46:53:04.633938N south: 34:44:13.536462N east: 68:50:28.1616W west: 94:51:40.938811W rows: 1458 cols: 3122 But gdal mis-reads it: tws:~$ gdalinfo tri_mean.asc Driver: GRASSASCIIGrid/GRASS ASCII Grid Files: tri_mean.asc Size is 3122, 1458 Coordinate System is `' Origin = (94.000,46.000) Pixel Size = (-0.008327994875080,-0.008230452674897) Corner Coordinates: Upper Left ( 94.000, 46.000) Lower Left ( 94.000, 34.000) Upper Right ( 68.000, 46.000) Lower Right ( 68.000, 34.000) Center ( 81.000, 40.000) Band 1 Block=3122x1 Type=Float32, ColorInterp=Undefined I also tried opening this map directly from Grass within QGIS using the Grass plugin. The problem persists - the projection of the map is flipped east to west when it appears in QGIS. Have I done something wrong somewhere, or is there a problem with the Grass 6.4 export or QGis/gdal import? Thanks! -- Tyler Smith plantarum.ca ___ Qgis-user mailing list Qgis-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-user
