3-Step postProcess sequence for SpatRasters using gdalwarp

DEFUNCT: Please use the postProcessTo functions.

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

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.

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

if (require("terra", quietly = TRUE)) {
  # prepare dummy data -- 3 SpatRasters, 2 SpatVectors
  # need 2 SpatRaster
  rf <- system.file("ex/elev.tif", package = "terra")
  elev1 <- terra::rast(rf)

  # 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
  utm <- "+proj=utm +zone=28 +datum=WGS84 +units=m +no_defs"
  vInUTM <- terra::project(vOrig, utm)
  vAsRasInLongLat <- terra::rast(vOrig, resolution = 0.008333333)
  res100 <- 100
  rInUTM <- terra::rast(vInUTM, resolution = res100, vals = 1)
  # crop, reproject, mask, crop a raster with a vector in a different projection
  #  --> gives message about not enough information
  t1 <- postProcessTo(elev1, to = vInUTM)
  # crop, reproject, mask a raster to a different projection, then mask
  t2a <- postProcessTo(elev1, to = vAsRasInLongLat, maskTo = vInUTM)
  t3a <- postProcessTo(elev1, to = rInUTM, maskTo = vInUTM)

}
#> terra 1.8.86
#> Running `postProcessTo`
#> cropping...
#> 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:  0.029 secs
#> masking...
#> done! took:  0.0383 secs
#> cropping...
#> done! took:  0.0211 secs
#> postProcessTo done! took:  0.14 secs
#> Running `postProcessTo`
#> Try setting options('reproducible.gdalwarp' = TRUE) to use a different, possibly faster, algorithm
#> cropping...
#> projecting...
#> done! took:  0.00594 secs
#> masking...
#> done! took:  0.0291 secs
#> cropping...
#> done! took:  0.0109 secs
#> postProcessTo done! took:  0.086 secs
#> Running `postProcessTo`
#> Try setting options('reproducible.gdalwarp' = TRUE) to use a different, possibly faster, algorithm
#> cropping...
#> projecting...
#> done! took:  0.138 secs
#> masking...
#> done! took:  0.0172 secs
#> cropping...
#> done! took:  0.0207 secs
#> postProcessTo done! took:  0.463 secs

3-Step postProcess sequence for SpatRasters using `gdalwarp`

Arguments

Details

See also

Examples