dgt_mosaic

G = dgt_mosaic(bbox; src_dir="", collection="MDS-2m", outfile="mosaic.tiff",
               inc=0, method="cubicspline", vrt="", proj="", verbose=1)

Mosaic downloaded DGT LIDAR tiles covering bbox into a single raster.

Reads all .tiff files in src_dir/collection/, builds an in-memory GDAL VRT mosaic, optionally clips to bbox, and writes the result to outfile — or returns it in memory when outfile="grid".

Note

Requires the HTTP package. Load it with using HTTP (or import HTTP) before calling dgt_mosaic.

Positional Argument

  • bbox: Bounding box [min_lon, max_lon, min_lat, max_lat] in WGS84 degrees.

Keyword Arguments

  • src_dir: Root directory of downloaded tiles (default: ~/.gmt/DGT). Prefix with _ to read from ~/.gmt/DGT/ — e.g. "_algarve" reads from ~/.gmt/DGT/algarve. When using a _-prefixed name, tiles from the default pool (~/.gmt/DGT/<collection>/) are transparently merged in as well.

  • collection: Collection subdirectory to mosaic (default: "MDS-2m"). One of "LAZ", "MDT-50cm", "MDS-50cm", "MDT-2m", "MDS-2m" (case-insensitive).

  • outfile: Output path (default: "mosaic.tiff"). Format is inferred from the extension:

    • .tiff / .tif — compressed GeoTIFF (DEFLATE, tiled 512×512).
    • .nc — compressed netCDF4 (NC4+DEFLATE).
    • "grid" — skip disk I/O entirely and return the result as a GMTgrid.

  • inc: If non-zero, resample the mosaic to this resolution in the raster’s CRS units (typically metres) via gdalwarp (default: 0, no resample).

  • method: Resampling algorithm used when inc != 0 or proj != "" (default: "cubicspline"). One of: near|bilinear|cubic|cubicspline|lanczos|average|rms|mode|min|max|med|q1|q3|sum. See the gdalwarp documentation for details.

  • vrt: If non-empty, also save the intermediate VRT mosaic to this file path (default: "", in-memory only).

  • proj: Reproject the mosaic to a different CRS (default: "", no reprojection). Accepts any GDAL-recognized CRS: a proj string ("+proj=utm +zone=29 +datum=WGS84"), an authority string ("EPSG:32629"), a bare EPSG number ("32629"), or the shorthand "geog" for EPSG:4326. Forces gdalwarp even when inc=0.

  • verbose: Verbosity level (default: 1). 0 = silent; 1 = progress messages; 2 = full detail.

Returns

  • When outfile="grid": a pixel-registered GMTgrid in memory.
  • Otherwise: nothing; the mosaic is written to outfile.

Notes

  • The mosaic is built with zero disk I/O for the intermediate step — the VRT lives in memory unless vrt is set.
  • When called from dgt_lidar with mosaic != "", the tile list is passed directly from the STAC query so only query-relevant tiles are mosaicked, not every file in src_dir.
  • Pixel registration is preserved: the returned grid matches the on-disk registration of the source tiles.

Examples

Mosaic tiles covering Lisbon already downloaded to the default directory:

using GMT, HTTP

dgt_mosaic([-9.2, -9.1, 38.7, 38.8]; src_dir="_lisboa")

Return mosaic as a GMTgrid in memory (no file written):

using GMT, HTTP

G = dgt_mosaic([-9.2, -9.1, 38.7, 38.8]; src_dir="_lisboa", outfile="grid")

Mosaic and reproject to UTM zone 29N:

using GMT, HTTP

dgt_mosaic([-9.2, -9.1, 38.7, 38.8]; src_dir="_lisboa", outfile="lisboa_utm.tiff",
           proj="EPSG:32629")

Source Code

View the source code for this function.

See Also

dgt_lidar, mosaic

For a complete worked example see the DGT LIDAR tutorial.