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splat-sdf

SPLAT! and Signal-Server terrain, made from your map regions' elevation

What it does

Makes SPLAT Data Files, the terrain SPLAT! and Signal-Server read, for every one-degree square your map regions touch, under /usr/local/share/hammunition/data/splat-sdf/: one file at one arc second (about 30 m, 36:37:116:117-hd.sdf.bz2, for splat-hd) and one at three (about 90 m, 36:37:116:117.sdf.bz2, for splat), with a link beside each under the name Signal-Server asks for (36_37_116_117-hd.sdf.bz2). Each is made from the elevation tiles Hammunition already downloaded and verified, with SPLAT's own converters, and kept compressed: both programs read the compressed files directly.

Why you would want it

SPLAT! and Signal-Server answer "what does the terrain do to this path" and "how far does this transmitter reach", and without terrain files both assume a flat earth at sea level and give a confident, worthless answer. SPLAT's documentation sends you to a retired USGS FTP server for SRTM tiles; this makes the same files from data already on the machine, so a coverage plot works with the network down.

Before it will work

osm-regions with at least one map region set (hammunition station set --map-regions ...); with none, this unit is deferred by name and the rest of its profile installs. dem-copernicus supplies the elevation; dem-3dep fetches nothing unless you choose USGS bare earth with hammunition station set --dem-source 3dep, and then the files are made from it. Run hammunition maps splat once as yourself to point SPLAT! at the directory through ~/.splat_path; or pass -d with the directory.

How it installs

  • converted from dem-copernicus by splat-sdf (Copernicus DEM licence (free, with attribution), https://copernicus-dem-30m.s3.amazonaws.com/readme.html)

Known problems

SPLAT's converters by default replace every elevation below sea level with its neighbours' average, which would turn Death Valley or a polder into dry land; Hammunition runs them with -n -32767, so only true voids are filled (measured on 2026-10-01). A square no installed tile covers, open sea for instance, has no file, and both programs then assume sea level there without stopping. splat-hd analyses at most 4 square degrees and splat 8, by their own build; a coverage plot wider than that needs splat, which reads the three-arc-second files. Measured on one Copernicus tile (Death Valley): about 15 s and 151 MB of memory at the peak to convert, 6.5 MB of files (5.7 MB at one arc second, 0.9 MB at three) where the uncompressed text would be 63 MB. Not yet run through hammunition install on a real region.

Keeping it current

  • probe: none
  • strategy: reinstall
  • Follows the elevation tiles: a new tile gets its files on the next install, a square no region needs loses them, and a change of --dem-source or of a tile's neighbours remakes the squares it touches.

Where to get help with the software itself

The file format and the converters are SPLAT!'s: its manual (man splat, the SPLAT DATA FILES section). For the elevation itself, see dem-copernicus and dem-3dep.

Source: catalog/packages/splat-sdf.yaml