[OSM-talk] Contours, hill shading, and holes problem

sylvain letuffe liste at letuffe.org
Tue Dec 30 20:30:01 GMT 2008


Hi,

It's probably right under my nose but I don't see it :

I followed :
http://wiki.openstreetmap.org/wiki/HikingBikingMaps

and still got trouble with :

1) 
I seam to have a projection problem with the raster hill shaded image 
generated by :
$ gdalwarp -of GTiff -co "TILED=YES" -srcnodata 32767 -dstnodata 
32767 -t_srs "+proj=merc +ellps=sphere +R=6378137 +a=6378137 
+units=m" -rcs -order 3 -tr 30 30 -multi alpes.tif alpes-mercator.tif
(+hillshading)

While contour lines are okay (I checked it with osm data I know) The hill 
shaded image is somehow shifted from north to south of about 40km

See here what I mean :
http://beta.letuffe.org/?zoom=12&lat=45.51228&lon=6.21422&layers=000000000B0

Unfortunelty, when it comes to mercator projection, I'm somehow level 0, If I 
am supposed to modify the line :
-t_srs "+proj=merc +ellps=sphere +R=6378137 +a=6378137" to get the good shift, 
could someone point me to a rather simple mercator first step ?


2)
Holes in the srtm data seams to be considered has -30000 meters, and thus 
giving me hugly artifact you can see in the upper link.
I thought the :
$ gdal_contour -snodata 32767
would get rid of them, but it seams that no

Same for the hill shading :
$ gdalwarp -srcnodata 32767 -dstnodata 32767
seams to have no effect

On the contour problem, I added 
"WHERE height>0" at the mapnik layer to get a little better, but I don't think 
that's the way to go

Many thanks for reading.

PS:I didn't know if talk or dev was the best place to go, so just tell me if I 
should move to dev

-- 
Sylvain Letuffe liste at letuffe.org
qui suis-je : http://slyserv.dyndns.org






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