I just discovered something very important. Simutrans uses the climate texture for snow, but it applies to it the lightmap.
(http://simutrans.svn.sourceforge.net/viewvc/simutrans/pak128/landscape/grounds/texture-lightmap.png?revision=1079)
Unlike what I believed, The lightmap isn't just pure 50% grey, but it's speckled. Hence, if you want your snow on the ground to merge seamlessly into the landscape, you must apply the same lightmap as well (grain merge layer mode in Gimp).
For your convenience, I made a texture after applying the lightmap (in attachment).
(http://forum.simutrans.com/index.php?action=dlattach;topic=11032.0;attach=20354)
This is especially important if you cover large parts of a tile ground with snow texture.
Ah, excellent observation, Fabio! It's very similar to the texture but the lightmap makes slight changes in the grain. Thanks for pointing this out and making a new template.
Thanks Fabio. I will apply it in my next work
Fabio
You have make a good Job with the Snow data.