# Explicit local DEM input

No DEM has been selected or downloaded. Supply a locally obtained single-band,
north-up GeoTIFF and a JSON metadata file. Do not modify original DEM bytes.
Store product URL/identifier, version, tile names, acquisition date, license and
vertical-datum evidence with the metadata. Obtain enough coverage around the
entire TMB Day 1 route for the selected horizon radius.

Required metadata fields (template only; replace every placeholder):

```json
{
  "source": "PRODUCT / VERSION / TILE / PROVIDER URL / LICENSE",
  "crs": "EPSG:REPLACE_WITH_VERIFIED_HORIZONTAL_CRS",
  "vertical_datum": "REPLACE_WITH_DOCUMENTED_VERTICAL_DATUM_OR_unknown",
  "elevation_unit": "m"
}
```

The CRS declaration must match the GeoTIFF. Metre elevations must be confirmed
from product documentation; missing raster unit tags are not independent evidence.
`unknown` explicitly records an unresolved vertical datum. A declaration is not
scientific validation. No geoid correction or vertical transformation is applied.
Use a cropped local raster: this prototype reads the band into memory. Raster
files in this directory are ignored by Git; metadata/documentation may be tracked.