Mixed UTM zones and terra collections

Native output

native <- bluertopo(
  aoi,
  resolution = "native",
  coverage = "fill",
  combine = "auto"
)

When selected rasters share a compatible grid, the result is a single terra::SpatRaster. When grids differ, the result is a terra::SpatRasterCollection with stable collection names derived from grid metadata.

class(native)

Requesting a collection

Use combine = "collection" when downstream code should always receive a collection, even for a single compatible grid.

collection <- bluertopo(
  aoi,
  resolution = "native",
  combine = "collection"
)

Requesting one output grid

Use combine = "single" together with output_crs and output_resolution when your analysis requires one grid. This is explicit resampling and is reported by a warning.

single <- bluertopo(
  aoi,
  resolution = "native",
  output_crs = "EPSG:26918",
  output_resolution = 10,
  combine = "single",
  resampling = c(
    elevation = "bilinear",
    uncertainty = "bilinear",
    contributor = "near"
  )
)

Geographic target resolutions are rejected in this release because degree-based cell sizes are ambiguous for bathymetric analysis. Use a projected CRS for explicit output grids.