3-Step postProcess sequence for SpatRasters using gdalwarp

gdalProject is a thin wrapper around sf::gdal_utils('gdalwarp', ...) with specific options set, notably, -r to method (in the ...), -t_srs to the crs of the toRas, -te to the extent of the toRas, -te_srs to the crs of the toRas, -dstnodata = NA, and -overwrite.

gdalResample is a thin wrapper around sf::gdal_utils('gdalwarp', ...) with specific options set, notably, "-r", "near", -te, -te_srs, tr, -dstnodata = NA, -overwrite.

gdalMask is a thin wrapper around sf::gdal_utils('gdalwarp', ...) with specific options set, notably, -cutline, -dstnodata = NA, and -overwrite.

gdalProject(
  fromRas,
  toRas,
  filenameDest,
  verbose = getOption("reproducible.verbose"),
  ...
)

gdalResample(
  fromRas,
  toRas,
  filenameDest,
  verbose = getOption("reproducible.verbose"),
  ...
)

gdalMask(
  fromRas,
  maskToVect,
  writeTo = NULL,
  verbose = getOption("reproducible.verbose"),
  ...
)

Arguments

fromRas: see from argument from postProcessTo(), but can only be a SpatRaster.
toRas: see to argument from postProcessTo(), but can only be a SpatRaster.
filenameDest: A filename with an appropriate extension (e.g., .tif) for gdal to write the output to. Since this function is conceived to be part of a chain, and not the final step, this function does not use writeTo, which is reserved for the final step in the chain.
verbose: Numeric, -1 silent (where possible), 0 being very quiet, 1 showing more messaging, 2 being more messaging, etc. Default is 1. Above 3 will output much more information about the internals of Caching, which may help diagnose Caching challenges. Can set globally with an option, e.g., options('reproducible.verbose' = 0) to reduce to minimal
...: For gdalProject, this can be method. For gdalMask can be destinationPath and touches. For all gdal*, this can also be and datatype.
maskToVect: see maskTo argument from maskTo(), but can only be a SpatVector
writeTo: Optional character string of a filename to use writeRaster to save the final object. Default is NULL, which means there is no writeRaster

Details

These three functions are used within postProcessTo, in the sequence: gdalProject, gdalResample and gdalMask, when from and projectTo are SpatRaster and maskTo is a SpatVector, but only if options(reproducible.gdalwarp = TRUE) is set.

This sequence is a slightly different order than the sequence when gdalwarp = FALSE or the arguments do not match the above. This sequence was determined to be faster and more accurate than any other sequence, including running all three steps in one gdalwarp call (which gdalwarp can do). Using one-step gdalwarp resulted in very coarse pixelation when converting from a coarse resolution to fine resolution, which visually was inappropriate in test cases.

Examples

# prepare dummy data -- 3 SpatRasters, 2 SpatVectors
# need 2 SpatRaster
rf <- system.file("ex/elev.tif", package = "terra")
elev1 <- terra::rast(rf)
#'
ras2 <- terra::deepcopy(elev1)
ras2[ras2 > 200 & ras2 < 300] <- NA_integer_
terra::values(elev1) <- rep(1L, terra::ncell(ras2))
#'
# a polygon vector
f <- system.file("ex/lux.shp", package = "terra")
vOrig <- terra::vect(f)
v <- vOrig[1:2, ]
#'
utm <- terra::crs("epsg:23028") # $wkt
vInUTM <- terra::project(vOrig, utm)
vAsRasInLongLat <- terra::rast(vOrig, resolution = 0.008333333)
res100 <- 100
rInUTM <- terra::rast(vInUTM, resolution = res100)
# crop, reproject, mask, crop a raster with a vector in a different projection
#  --> gives message about not enough information
t1 <- postProcessTo(elev1, to = vInUTM)
#> Running `postProcessTo`
#>  cropping...
#>  done! took:  0.0759 secs
#>  projecting...
#>  
#>  projectTo is a Vector dataset, which does not define all metadata
#>    required.
#>  Using the origin and extent from `ext(from)` in the projection from
#>    `crs(projectTo)`.
#>  If this is not correct, create a template gridded object and pass
#>    that to `projectTo`...
#>  
#>  done! took:  0.489 secs
#>  masking...
#>  done! took:  0.0372 secs
#>  cropping...
#>  done! took:  0.0198 secs
#> postProcessTo done! took:  0.655 secs
# crop, reproject, mask a raster to a different projection, then mask
t2a <- postProcessTo(elev1, to = vAsRasInLongLat, maskTo = vInUTM)
#> Running `postProcessTo`
#> Try setting options('reproducible.gdalwarp' = TRUE) to use a different, possibly faster, algorithm
#>  cropping...
#>  done! took:  0.0215 secs
#>  projecting...
#>  done! took:  0.0293 secs
#>  masking...
#>  done! took:  0.0113 secs
#>  cropping...
#>  done! took:  0.0111 secs
#> postProcessTo done! took:  0.107 secs


# using gdal directly --> slightly different mask
opts <- options(reproducible.gdalwarp = TRUE)
t2b <- postProcessTo(elev1, to = vAsRasInLongLat, maskTo = vInUTM)
#> Running `postProcessTo`
#>  using sf::gdal_utils('warp') because
#>    options("reproducible.gdalwarp" = TRUE) ...
#>  running gdalProject ...
#>  done! took:  0.0249 secs
#>  running gdalResample ...
#>  done! took:  0.239 secs
#>  running gdalMask ...
#>  done! took:  0.0427 secs
#> postProcessTo done! took:  0.31 secs
t3b <- postProcessTo(elev1, to = rInUTM, maskTo = vInUTM)
#> Running `postProcessTo`
#>  using sf::gdal_utils('warp') because
#>    options("reproducible.gdalwarp" = TRUE) ...
#>  running gdalProject ...
#>  done! took:  0.0488 secs
#>  running gdalResample ...
#>  done! took:  0.034 secs
#>  running gdalMask ...
#>  done! took:  0.115 secs
#> postProcessTo done! took:  0.201 secs
options(opts)

3-Step postProcess sequence for SpatRasters using `gdalwarp`

Arguments

Details

See also

Examples