[gdal-dev] gdaldem hillshade returns an empty .tif (i.e. everything is 181 (?))

[Even Rouault]

Le mardi 30 juin 2015 19:05:58, Ruth Simm a écrit :
> Hm. Well the prj is 3857 ...but I reprojected it from 4326....would -
> 
> I did run this on one tile - came out fine:
> gdaldem hillshade DCM_N00E116.tif hillshade_test.tif -compute_edges -z 5 -s
> 111120 -az 90 but this returned the same result on the global file:
> 
> gdaldem hillshade -of GTiff infile_3857.tif hillshade.tif -compute_edges -z
> 5 -s 111120 -az 90

For EPSG:3857, you shouldn't add  -s 111120 as the horizontal units are 
already meters.

> 
> 
> 
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> 
>      On Tuesday, June 30, 2015 2:41 AM, Even Rouault
> <even.rouault at spatialys.com> wrote:
> 
> 
>  #yiv0977550860 p, #yiv0977550860 li {white-space:pre-wrap;}Le mardi 30
> juin 2015 01:20:13, Ruth Simm a écrit :> I ran this command on a
> completely NORMAL (but large) global .tiff with a> few tiles missing - but
> nothing else suspicious - and after 40 minutes it> returned a dud file
> with '181' being the only value. Has this ever> happened to anyone
> before?> gdaldem hillshade -of GTiff infile.tif hillshd.tifRuth,I guess
> this might be an issue with the ratio of vertical units to
> horizontal.http://gdal.org/gdaldem.html#gdaldem_hillshade:-s scale:ratio
> of vertical units to horizontal. If the horizontal unit of the source DEM
> is degrees (e.g Lat/Long WGS84 projection), you can use scale=111120 if
> the vertical units are meters (or scale=370400 if they are in feet) I'd
> suggest you experiment a bit on a subwindow of your big raster or a
> subsampled version of it first.Even-- Spatialys - Geospatial professional
> serviceshttp://www.spatialys.com

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