On 02/08/16 17:24, Veronica Andreo wrote:
Hi Helli,
2016-08-02 11:37 GMT-03:00 Helmut Kudrnovsky <[email protected]
<mailto:[email protected]>>:
>as they are in mercator projection (epsg:3857) and I'm working in
eu_laea
I assume eu_laea is epsg: 3035 (http://epsg.io/3035)?
if yes, epsg3035 is dedicated to the area of Europe.
is the generalized coastlines data for the whole world?
yes and yes
maybe world wide data in epsg:3857 (http://epsg.io/3857) can't be
reprojected into a epsg:3035 location without too much distortion?
mhm... I see... and it makes sense...
my workflow in such cases where only a subregion of worldwide data
is needed
: I use the clip mechanism of ogr2ogr [1] in order to clip out my
region and
reproject only this clipped area.
HTH
it does, indeed :) (I wonder what is qgis using then to make the global
data re-projection...)
I also tried with clipping to my region inside v.import (which is maybe
equivalent to your trick with ogr2ogr?), but got the same error every
time... boh... would be anyway useful to clarify what this "datum_trans"
option means.
I can confirm the issue when using v.in.ogr + v.proj, when using the
file to define the location:
grass73 -c
/data/GEODATA/OSM/coastlines-generalized-3857/coastlines_z8.shp
/data/GRASS/DATA7/test_3857/
v.in.ogr /data/GEODATA/OSM/coastlines-generalized-3857/coastlines_z8.shp
and then in the EPSG 3035 location:
v.proj location=test_3857 mapset=PERMANENT input=coastlines_z8
Reprojecting primitives ...
ATTENTION: pj_transform() a échoué: failed to load datum shift file
ERREUR :Unable to re-project vector map <coastlines_z8@PERMANENT> from
<test_3857>
However, when I create the 3857 location using the EPSG code, it works:
grass73 -c epsg:3857 /data/GRASS/DATA7/test_3857_epsg/
[...]
v.proj location=test_3857_epsg mapset=PERMANENT input=coastlines_z8
success.
There is a difference in the projection definition between the two:
diff -u test_3857/PERMANENT/PROJ_INFO test_3857_epsg/PERMANENT/PROJ_INFO
--- test_3857/PERMANENT/PROJ_INFO 2016-08-02 18:24:25.965809631 +0200
+++ test_3857_epsg/PERMANENT/PROJ_INFO 2016-08-02 18:28:18.427085934 +0200
@@ -7,7 +7,5 @@
x_0: 0.0
y_0: 0
k: 1.0
-nadgrids: @null
wktext: defined
no_defs: defined
-over: defined
Erasing the 'nadgrids: @null' from the first allows to reproject.
The .prj file of the original shapefile contains:
EXTENSION["PROJ4","+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0
+lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m +nadgrids=@null +wktext
+no_defs +over"]
I guess the issue comes from how this is handled...
Moritz--
Département Géosciences, Environnement et Société
Université Libre de Bruxelles
Bureau: S.DB.6.138
CP 130/03
Av. F.D. Roosevelt 50
1050 Bruxelles
Belgique
tél. + 32 2 650.68.12 / 68.11 (secr.)
fax + 32 2 650.68.30
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