[GRASS-user] r.proj issue

[Markus Metz]

On Sat, Sep 14, 2019 at 1:15 AM Helmut Kudrnovsky <hellik at web.de> wrote:
>
> Rich Shepard wrote
> > Reprojecting a 10m DEM fails. Following are the command and input/output
> > projection and map description information. Screenshots of the input and
> > output maps are attached.
> >
> > I need to understand why the output is wrong.
> >
> > Command:
> > r.proj loc=Oregon map=topography in=n46w123 met=lanczos_f mem=16000 --o
> >
> > Input location:
> > name: unnamed
> > ellps: grs80
> > proj: lcc
> > lat_1: 46
> > lat_2: 44.33333333333334
> > lat_0: 43.66666666666666
> > lon_0: -120.5
> > x_0: 2500000
> > y_0: 0
> > no_defs: defined
> > unit: Meter
> > units: Meters
> > meters: 1
> >
> > Cols: 502 (80961)
> > Rows: 39234 (113148)
> > North: 262349.035904 (262349.035904)
> > South: 223115.062541 (149201.112724)
> > West: 2302891.866970 (2302891.866970)
> > East: 2303393.867032 (2383852.876897)
> > EW-res: 1.000000
> > NS-res: 0.999999
> >
> > Output location:
> > name: NAD83(HARN) / Oregon North
> > datum: nad83harn
> > ellps: grs80
> > proj: lcc
> > lat_1: 46
> > lat_2: 44.33333333333334
> > lat_0: 43.66666666666666
> > lon_0: -120.5
> > x_0: 2500000
> > y_0: 0
> > no_defs: defined
> > unit: meter
> > units: meters
> > meters: 1
> >
> > Cols: 500 (71702)
> > Rows: 39232 (50757)
> > North: 262348.951018 (273873.984569)
> > South: 223116.836808 (223116.836808)
> > West: 2302892.017711 (2231689.553588)
> > East: 2303392.020970 (2303392.020970)
> > EW-res: 1.000007
> > NS-res: 1.000003Cols: 500 (71702)
> > Rows: 39232 (50757)
> > North: 262348.951018 (273873.984569)
> > South: 223116.836808 (223116.836808)
> > West: 2302892.017711 (2231689.553588)
> > East: 2303392.020970 (2303392.020970)
> > EW-res: 1.000007
> > NS-res: 1.000003
> >
> > Rich
> > _______________________________________________
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>
> > grass-user at .osgeo
>
> > https://lists.osgeo.org/mailman/listinfo/grass-user
> >
> > input-dem.png (296K)
> > <
http://osgeo-org.1560.x6.nabble.com/attachment/5416106/0/input-dem.png>
> > output-dem.png (28K)
> > <
http://osgeo-org.1560.x6.nabble.com/attachment/5416106/1/output-dem.png>
>
> a good thing to see if reprojection of raster data works correctly, is
> comparing before/after r.proj with gdalwarp (1) results.

gdalwarp estimates the target extents unless you use the -te option. In
contrast, r.proj uses the current region. r.proj can estimate the target
extents with the -p or -g flag. I suggest to first check you current region
in the target location/mapset and compare with r.proj -p or -g

Markus M
>
> (1) https://gdal.org/programs/gdalwarp.html#gdalwarp
>
>
>
>
> -----
> best regards
> Helmut
> --
> Sent from: http://osgeo-org.1560.x6.nabble.com/Grass-Users-f3884509.html
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