Binary mask by Euclidean distance from features

Computes Euclidean distance from non-NA cells in a raster and returns a binary mask where distance is within the threshold. Useful for constraining analysis to a corridor around streams (e.g., max_width parameter in VCA).

Usage

fl_mask_distance(x, threshold)

Arguments

x

A SpatRaster where non-NA cells are the features to measure distance from (e.g., rasterized streams).

threshold

Numeric. Maximum distance in map units (e.g., metres). Cells within this distance are 1; cells beyond are 0.

Value

A SpatRaster with values 1 (within threshold) and 0 (beyond).

Details

Distance is computed with terra::distance() which calculates Euclidean distance from the nearest non-NA cell. Feature cells themselves receive distance 0 and are always included in the mask.

Examples

dem <- terra::rast(system.file("testdata/dem.tif", package = "flooded"))
streams <- sf::st_read(
  system.file("testdata/streams.gpkg", package = "flooded"),
  quiet = TRUE
)
stream_r <- fl_stream_rasterize(streams, dem, field = "upstream_area_ha")
corridor <- fl_mask_distance(stream_r, threshold = 1000)
terra::plot(corridor, col = c("grey90", "steelblue"), main = "Within 1 km of stream")