Question about missing .hgt files

[cviebrock]

I'm trying to use your scripts and am running into trouble, but probably because of something I'm doing wrong:

python heightmap.py --elevation-dir ./data \
    --geojson ~/Downloads/buildings.json \
    --output my.heightmap \
    --save-image my.png \
    49.897 -97.137 4 512

The output is:

ll 49.897 -97.137 4.0 512 <pyproj.Proj object at 0x10e8a9390>
Traceback (most recent call last):
  File "heightmap.py", line 90, in <module>
    elev = SrtmHeightMap(lat, lng, resolution, size, proj, args.elevation_dir)
  File "heightmap.py", line 49, in __init__
    tiles[tile_key] = SrtmHeightMap._loadTile(data_dir, lat, lng)
  File "heightmap.py", line 65, in _loadTile
    with open(p, 'rb') as f:
IOError: [Errno 2] No such file or directory: './data/N90E014.hgt'

I figured that I'd only need an .hgt file for the area I'm trying to map (i.e. N49W097.hgt), but the script is looking for a different file. Furthermore, I don't think there actually are any files for N90*.

Where did I mess up? 😉

[perliedman]

Hi there!

It's been quite a while since I used this myself, but it looks like you're missing a projection definition. If you look at the docs for heightmap.py, it takes a --projection argument. Without it, I guess it uses some default that's not suitable for your coordinates.

A suitable projection would probably be the UTM zone you're in, for example.