dgt_lidar

dgt_lidar(bbox; user="", password="", save=false, output_dir="", delay=1.0, collection="MDS-2m",
          dry=false, latest=true, mosaic="", inc=0, method="cubicspline", compress="tif",
          proj="", verbose=1)
dgt_lidar(lon, lat; neighbors=0, ...)
dgt_lidar(GI::Union{GMTgrid,GMTimage}; ...)
dgt_lidar(lon::AbstractVector, lat::AbstractVector; ...)
dgt_lidar(D::GMTdataset; zoom=0, ...)

Download LIDAR tiles from Portugal’s national elevation survey via the DGT CDD STAC API.

Authenticates against the DGT (Direção-Geral do Território) Collaborative Data Distribution (CDD) portal (https://cdd.dgterritorio.gov.pt/) and downloads all tiles intersecting the given bounding box. Tiles are organized into subdirectories by collection name. Downloads are resumable — existing files are skipped automatically.

Note

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

Positional Arguments — Six Accepted Forms

  • bbox: A 4-element array or tuple [min_lon, max_lon, min_lat, max_lat] in WGS84 degrees.

  • [lon, lat] (2-element array): Downloads only the tile containing the given point. Use neighbors to include surrounding tiles and zoom to set the tile-grid size.

  • lon, lat (two scalars): Same as the 2-element form, using separate scalar arguments.

  • GI: A GMTgrid or GMTimage with a valid projection. The geographic extent is extracted from the grid/image header; non-geographic projections are reprojected to lon/lat automatically.

  • lon, lat (two vectors): Separate [min, max] vectors or matrices for longitude and latitude.

  • D: A GMTdataset (e.g. from geocoder). The geographic bounding box stored in D.ds_bbox is used. The optional zoom keyword (default 0) enlarges the query to tile boundaries at the specified zoom level via mosaic.

Keyword Arguments

  • user: DGT CDD account e-mail. If omitted, read from ~/.dgt.

  • password: DGT CDD account password. If omitted, read from ~/.dgt. The ~/.dgt file format (first line is a comment):

    # Login data for the DGT LIDAR downloads
login your@email.pt
password your_password

  • save: If true, save user and password to ~/.dgt for future use (default: false).

  • output_dir: Root directory for downloaded files (default: ~/.gmt/DGT). Prefix with _ to write inside ~/.gmt/DGT/ — e.g. "_algarve" saves to ~/.gmt/DGT/algarve.

  • delay: Seconds between requests (default: 1.0). Increase to avoid server throttling.

  • collection: Collection to download. One of "LAZ", "MDT-50cm", "MDS-50cm", "MDT-2m", "MDS-2m". Case-insensitive. Default "MDS-2m" (Digital Surface Model at 2 m resolution).

  • dry: If true, query the API and print found files but skip all downloads (default: false).

  • neighbors: Number of neighboring DGT tiles to include around a single-point query (default: 0 = only the tile containing the point). Can be an integer N (giving a (2N+1)×(2N+1) grid of tiles) or a 2-element vector [Nx, Ny] for asymmetric east-west/north-south expansion. Only used with the 2-element or scalar point forms.

  • zoom: OSM zoom level used only as a fallback when the STAC API cannot determine the central tile’s bounding box (default: 14). Under normal conditions this has no effect.

  • latest: If true (default), keep only the most recent version of each tile when multiple versions exist. DGT names versioned files with a _v01, _v02, … suffix; the unversioned original is treated as version 0. Set to false to download every version.

  • compress: Output format for downloaded tiles. "tif" (default) = compressed GeoTIFF (DEFLATE + 512×512 tiling); "nc" = compressed netCDF4 (NC4+DEFLATE); "" = write as-is (uncompressed GeoTIFF). Reduces on-disk size significantly. Not applied to LAZ files.

  • mosaic: Controls the mosaic output after downloading (default: "" = no mosaic).

    • "" — download only, no mosaic.
    • "grid" — assemble and return a GMTgrid in memory (no disk I/O).
    • "path/to/file.tiff" — write a compressed GeoTIFF to disk.
    • "path/to/file.nc" — write a compressed netCDF4 file to disk. Ignored when dry=true. See also the inc, method, and proj keywords.

  • inc: Resample resolution for the mosaic in CRS units (metres). 0 = no resample (default: 0). Used only when mosaic != "".

  • method: Resampling algorithm when inc != 0 (default: "cubicspline"). One of: near|bilinear|cubic|cubicspline|lanczos|average|rms|mode|min|max|med|q1|q3|sum. Used only when mosaic != "".

  • 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 (errors only); 1 = downloaded file names; 2 = full progress including sub-query details.

Notes

  • Large bounding boxes are auto-subdivided into ~200 km² sub-queries to stay within API limits.
  • Session re-authenticates automatically every 25 minutes or every 10 files downloaded.
  • Files are streamed directly to disk — no RAM bottleneck on large tiles.
  • The mosaic step uses only the tiles returned by the STAC query, not every file in output_dir.

Credits

Inspired by the dgtcd_downer Python package, heavily reworked and extended to fit the GMT.jl API style.

Examples

Save credentials to ~/.dgt (optional, avoids passing them each time):

using GMT, HTTP

dgt_lidar(rand(4), user="nome@email.pt", password="password", save=true)

Download the DSM tiles at 50 cm resolution covering the Lisbon area and save to a custom subdirectory:

using GMT, HTTP

dgt_lidar([-9.2, -9.1, 38.7, 38.8]; output_dir="_lisboa", collection="MDT-50cm")

Download the tile containing a single point and return the mosaic as a GMTgrid in memory:

using GMT, HTTP

G = dgt_lidar(-7.607, 40.322; mosaic="grid")

Download a 3×3 neighborhood of tiles around a point and save mosaic as GeoTIFF:

using GMT, HTTP

dgt_lidar(-7.607, 40.322; neighbors=1, mosaic="estrela.tiff")

For a complete worked example see the DGT LIDAR tutorial.

Precompiling packages...

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Source Code

View the source code for this function.

See Also

dgt_mosaic, mosaic, geocoder