* download all the diles requested.
* better support for depressions below sea level.
* use wget instead of urllib, because it has 9so far) better support for continuing a download.
* handle when the data requested goes outside SRTM's coverage.
+ -n|--dry-run.
+ head() the output of osmpbf_outline(), so the latter does not scans the whole file. it's better for files for big areas (f.i., europe).
* boo.
+ two svg's for things not rendered by OSM.
+ another svg for things not rendered by OSM.
+ script for importing OSM data to the official OSM db.