The relief (hillshading) layer on OpenSnowMap.org have been updated. On the major part of the world, resolution jumps to 30m instead of 90m beforehand, thanks to the ongoing release of 1 arc-second SRTM data by NASA.

30m_-_90m.png
To mak a long story short, the relief is more precise by a x1.5 zoom factor.

For more details, here are the data used on the serveur to generate the hillshading.
DEM3_coverage.png
Screenshot from USGS explorer on Google-map background

30m SRTM data are used where available. Up north, data comes from the EU-DEM for scandinavia, ASTER for Alaska, Canada, Greenland and Russia. In an area extending from Greece to Iran, I had to kept the 90m SRTM data from CGIAR, I hoipe to be able to update this area soon.

To assemble those datasets, I use a script based on python-gdal to merge the data by small 1x1° tiles, filtering SRTM data by a 3x3 average filter and ASTER by a 10x10 filter to reduce noise. Gdal utilities then re-assemble everything in a big Tiff. For rendering, I took the opportunity to pré-calculate smaller Tiff at lower zooms to reduce the load on the tile server. The map should show up more fluidly.

Contour lines will be updated from the same datasets, if I can optimize them enough to fit my disks.