Convert raster to lines — rasterToLineSegments • roads

Converts rasters that represent lines into an sf object.

Usage

rasterToLineSegments(rast, method = "mst")

Arguments

rast: SpatRaster. Raster representing lines all values > 0 are assumed to be lines
method: character. Method of building lines. Options are "mst" (default) or "nearest". See Details below.

Value

an sf simple feature collection

Details

For method = "nearest" raster is first converted to points and then lines are drawn between the nearest points. If there are two different ways to connect the points that have the same distance both are kept which can cause doubled lines. USE WITH CAUTION. method = "mst" converts the raster to points, reclassifies the raster so roads are 0 and other cells are 1 and then uses projectRoads to connect all the points with a minimum spanning tree. This will always connect all raster cells and is slower but will not double lines as often. Neither method is likely to work for very large rasters

Examples

CLUSexample <- prepExData(CLUSexample)
# works well for very simple roads
roadLine1 <- rasterToLineSegments(CLUSexample$roads)
#> Warning: No 0s detected in weightRaster. If existing roads have not been included in the weightRaster set roadsInWeight = FALSE to have them burned in

# longer running more realistic examples
# \donttest{
demoScen <- prepExData(demoScen)
# mst method works well in this case
roadLine2 <- rasterToLineSegments(demoScen[[1]]$road.rast)
#> Warning: No 0s detected in weightRaster. If existing roads have not been included in the weightRaster set roadsInWeight = FALSE to have them burned in

# nearest method has doubled line where the two roads meet
roadLine3 <- rasterToLineSegments(demoScen[[1]]$road.rast, method = "nearest")

# The mst method can also produce odd results in some cases
roadLine4 <- rasterToLineSegments(demoScen[[4]]$road.rast)
#> Warning: No 0s detected in weightRaster. If existing roads have not been included in the weightRaster set roadsInWeight = FALSE to have them burned in

# }