[GRASS-user] shaded relief of srtm tiles

[thorsten]

thank you Hamish,

patching works fine  ( http://www.flickr.com/photos/h2guide/329431459 ),
but i try to create a shaded relief of a hughe area,
so i will have to process it tile by tile.

what i am actually doing is:

r.in.srtm input=N42W005 output=tile  #r.in.srtm input=N42W004 output=tile
g.region rast=tile
r.colors map=tile rules=srtm
r.shaded.relief map=tile shadedmap=relief altitude=44 azimuth=270 
units=meters
r.his h_map=tile i_map=relief r_map=final.red g_map=final.green 
b_map=final.blue
r.composite red=final.red green=final.green blue=final.blue levels=32 
output=final;

"final" is the shaded and colored relief.

what do you mean by "absolute" color table?
i am  using the  predefined color table "srtm"
and the result is still different for the adjacent tiles:

http://www.flickr.com/photos/h2guide/329431463

pasting the colored maps (called "tile") together looks ok:
 
http://www.flickr.com/photos/h2guide/329472914

so the problem is the greyscale component (called "relief") produced by 
r.shaded.relief:

http://www.flickr.com/photos/h2guide/328146671

What should I do to get seamless tiles?

Thorsten


Hamish wrote:

>thorsten wrote:
>  
>
>>hello list,
>>
>>i try to use r.shaded.relief  on srtm tiles imported with r.in.srtm.
>>the results look nice, but adjacent tiles have a different average 
>>brightness.
>>I used the same parameters (altitude=44 azimuth=270 units=meters) for 
>>both maps and tried with grass versions 6.02 and 6.20
>>That's how it looks like for the original srtm tiles N42W005.hgt.zip
>>and N42W004.hgt.zip:
>>http://www.flickr.com/photos/h2guide/328146671/
>>
>>What am i doing wrong? (Or what am i supposed to do in order to produce 
>>seamless shaded reliefs?)
>>    
>>
>
>
>try setting an absolute color table with r.colors,
>
>
>or merge the two tiles first:
>
>g.region rast=tile1,tile2
>r.patch in=tile1,tile2 out=tile_merge
>
>
>Hamish
>
>  
>