- the old version just draws fixed-size boxes in any zoom. in high zoom
modes, this results in sparse boxes all over the screen. the new
version scales these boxes so they fill the area completely. this
works for both absolute and height gradient
- change of DEM source path from /srtm/version2_1/SRTM3/OLD/ to
/srtm/version2_1/SRTM3/. again, yes. that's because the first is not
working but the second is.