dem-qmapshack¶
Hillshade, slope and 20 m contour lines for QMapShack, from the elevation tiles
- Version recorded: station
- Categories:
navigation-maps - Upstream: https://gdal.org/
- Needs first:
dem-copernicus,dem-3dep,gdal-bin
What it does¶
Builds two things QMapShack reads, under /usr/local/share/hammunition/data/dem-qmapshack/: dem/dem.vrt, one virtual raster over every elevation tile, from which QMapShack draws hillshade and slope and reads heights for track profiles; and contours/contours.vrt, plain 20 m contour lines drawn per tile with GDAL, which QMapShack lists as a map to lay over the others.
Why you would want it¶
QMapShack does not draw contour lines from elevation itself, and needs its elevation as one virtual raster. This makes both from the tiles, with the archive's GDAL and nothing else.
Before it will work¶
dem-copernicus, dem-3dep and gdal-bin, which install first. dem-3dep fetches nothing unless you choose it with hammunition station set --dem-source 3dep; then the elevation and contours are drawn from USGS 3DEP bare earth instead of Copernicus, and a region outside the US gets no elevation in QMapShack while that is chosen.
How it installs¶
- converted from dem-copernicus by gdal-dem (Copernicus DEM licence (free, with attribution), https://copernicus-dem-30m.s3.amazonaws.com/readme.html)
Known problems¶
The contours are unlabelled lines at a fixed resolution: legible, not pretty. Labelled contours inside the map need a tool the archive does not carry. Measured on one mountain tile on 2026-09-28: 4 s and a 97.8 MB GeoPackage to trace, 1.5 s and 5.4 MB to rasterise; the GeoPackage is removed once rasterised. QMapShack 1.17.1 draws hillshade from the elevation (confirmed on the field laptop on 2026-09-29, at the 3 km and 10 km scales); slope shading has not yet been tried there. From 3DEP the contours are rasterised at 10,812 pixels a tile to keep its 10 m detail: measured on one Shenandoah tile on 2026-10-01, 17.3 s and a 212 MB GeoPackage to trace, 3.4 s and 8.4 MB to rasterise. QMapShack drawing a 3DEP elevation has not been measured.
Keeping it current¶
- probe: none
- strategy: reinstall
- Follows dem-copernicus: a new tile gets contours on the next install and both virtual rasters are rebuilt when the set of tiles changes.
Where to get help with the software itself¶
The GDAL documentation (https://gdal.org/) for the tools; QMapShack's wiki (https://github.com/Maproom/qmapshack/wiki) for how it shows them.