Layers, contributor values, and RAT metadata

BlueTopo source GeoTIFFs currently include elevation, vertical uncertainty, and contributor/source identifier bands. bluertopo exposes those as canonical layer names.

Elevation only

elevation <- bluertopo(
  aoi,
  layers = "elevation"
)

All canonical layers

all_layers <- bluertopo(
  aoi,
  layers = "all",
  details = TRUE
)

names(all_layers$data)

The contributor band contains numeric identifiers. Interpret those identifiers with the NOAA RAT sidecar metadata and source documentation. bluertopo can download RAT sidecars with the original assets, but it does not currently normalize contributor tables into a package-level lookup.

NOAA’s BlueTopo product page is the package’s primary external reference: https://nauticalcharts.noaa.gov/data/bluetopo.html.

assets <- bluertopo_download(
  aoi,
  path = file.path(tempdir(), "bluertopo-downloads"),
  rat = TRUE
)

subset(assets, asset_type == "rat")

Vertical-reference metadata

bluertopo(details = TRUE) includes vertical-reference text discovered by terra/GDAL metadata inspection when available.

result <- bluertopo(aoi, details = TRUE)
result$provenance$vertical_reference_text