[GRASS-user] r.proj issue

[Markus Metz]

On Sun, Sep 15, 2019 at 8:39 PM Rich Shepard <rshepard at appl-ecosys.com>
wrote:
>
> On Sat, 14 Sep 2019, Markus Metz wrote:
>
> > 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, et al.:
>
> I've worked on this for 2+ days and cannot get the DEM from the source
> location to the target location when both have the same projection and
> units.
>
> Following the above still fails and I've no idea what to do now.
>
> Source location:
> > r.proj -p loc=Oregon map=topography in=n45w121
> Input map <n45w121 at topography> in location <Oregon>:
> Source cols: 80297
> Source rows: 111356
> Local north: 148340.8192959
> Local south: 36984.78211177
> Local west: 2459852.09770149
> Local east: 2540149.13365527
>
> Current (target) region:
> > g.region -p
> projection: 99 (NAD83(HARN) / Oregon North)
> zone:       0
> datum:      nad83harn
> ellipsoid:  grs80
> north:      307220.87234928
> south:      -199204.29675669
> west:       2161358.9640483
> east:       2822158.25992759
> nsres:      1.00000033
> ewres:      1.00000045
> rows:       506425
> cols:       660799
> cells:      334645133575
>
> Reset current region to the source:
> > g.region n=148340.8192959 s=36984.78211177 w=2459852.09770149
e=2540149.13365527 cols=80297 rows=111356

You should now use
r.proj loc=Oregon map=topography in=n45w121

and not r.unpack, that is a completely different workflow that has nothing
to do with reprojection.

Markus M

>> Unpack the DEM in the current location/mapset;
> > r.unpack n45w121.pack
> WARNING: Difference between PROJ_INFO file of packed map and of current
>           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
>           - towgs84: 0.000,0.000,0.000
> ERROR: Projection of dataset does not appear to match current location. In
>         case of no significant differences in the projection definitions,
>         use the -o flag to ignore them and use current location
definition.
>
> If I correctly understand gdalwarp it functions like r.proj in
reprojecting
> a raster map from one location to another location. Here, both the source
> and target locations have the same projection. Will gdalwarp work in this
> case? Isn't r.pack/r.unpack the correct module pair?
>
> Please advise me of what I should do now or what other information I can
> provide.
>
> Regards,
>
> Rich
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