Mixed grids and output grid

This example uses BlueTopo source tiles from the National Bathymetric Source catalog. The build verifies the downloaded assets and records their source metadata.

New York Harbor is the primary public AOI for the examples, but its current small plan is a compatible 4 m grid. This example uses BlueTopo tiles covering Key West and Boca Chica Channel because the documented secondary AOI currently intersects 4 m and 8 m source grids and therefore demonstrates mixed native-grid behavior.

Mixed native grids are preserved unless the user asks for a single output grid. combine = "single" needs an explicit output grid when native grids are incompatible. Resampled uncertainty values are not original source cells, and contributor resampling must be nearest-neighbor.

Example area

Native mixed-grid extraction

native <- bluertopo(
  real_aoi,
  resolution = "native",
  coverage = "fill",
  combine = "auto",
  details = TRUE,
  progress = FALSE,
  quiet = TRUE
)

if (!inherits(native$data, "SpatRasterCollection")) {
  stop("The documented real AOI no longer produces mixed native grids.", call. = FALSE)
}

Output object	Grid	CRS	Resolution	Source count	Layers
SpatRasterCollection	grid_01_epsg26917_4x4	EPSG:26917	4 x 4	1	elevation
SpatRasterCollection	grid_02_epsg26917_8x8	EPSG:26917	8 x 8	1	elevation

Native grid footprints

BlueTopo tile coverage selected for the Key West mixed-grid example area.

Explicit single output grid

single <- suppressWarnings(bluertopo(
  real_aoi,
  layers = "elevation",
  resolution = "native",
  coverage = "fill",
  output_crs = "EPSG:26917",
  output_resolution = 100,
  combine = "single",
  details = TRUE,
  progress = FALSE,
  quiet = TRUE
))

Output object	CRS	Resolution	Extent	Resampled
SpatRaster	EPSG:26917	100 x 100	415613, 418713, 2744703.3, 2748003.3	Yes

BlueTopo elevation resampled to the specified output grid.

The explicit grid is useful for workflows that require one raster, but it is a resampling operation. Native source-resolution selection remains separate from output-grid creation.