Build overview pyramids for a .vec raster — vec_build

Appends n_levels - 1 reduced-resolution copies of the raster to the file. Each level is computed by 2x downsampling the previous level with the chosen kernel. Reading via vec_read_window(level = L) picks tiles at level L; the file's n_levels is updated in place.

Usage

vec_build_overviews(
  path,
  levels,
  resampling = c("average", "nearest", "bilinear", "mode", "gauss"),
  compression = c("fast", "balanced", "max")
)

Arguments

path: Path to a .vec raster file. The file is modified in place.
levels: Total levels including level 0 (so levels = 5 adds four overviews: levels 1..4). Must be in [2, 16].
resampling: One of "nearest", "average", "bilinear", "mode", "gauss". "average" is the right choice for continuous rasters; "mode" for categorical/land-cover.
compression: Compression effort for the new tiles. Defaults to "fast" because overview tiles are usually one-shot writes.

Value

Invisible NULL.

Details

Unlike the streamed raster verbs, this decodes every band of the base raster into memory at once to build the pyramid, so peak memory is on the order of the full base raster (all bands). Build overviews before a raster grows past what fits in RAM, or on a per-band basis for very large stacks.