# Mixed grids and output grid

In CRAN or offline builds, network-dependent chunks are not evaluated.

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)
    }

## Native grid footprints

## 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
    ))

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.