Import a contiguous raster map — importMap • lbmech

Import a raster for a specific region from a multisource environment, such as the outputs of the getMap function.

importMap(
  region,
  polys,
  tile_id = "TILEID",
  z_fix = NULL,
  neighbor_distance = 5,
  FUN = NULL,
  mask = FALSE,
  vals = "location",
  filt = 0,
  z_min = NULL,
  dir = tempdir(),
  ...
)

Arguments

region: A SpatRaster, Raster*, SpatVector, Spatial* or character string representing the area of interest
polys: A polygon of class SpatVector representing the partitioning grid for the maximum possible area, in the same format as the output of the makeGrid function.
tile_id: A character string representing the name of the column in the polys polygon pontaining the unique Tile IDs. Default is tile_id = 'TILEID'
z_fix: A SpatRaster or Raster* object with the desired output projection, resolution, and origin. Required if tiles is of classes SpatVector, Spatial*, or character, unless res is provided.
neighbor_distance: An integer representing the number of cells that tiles are buffered. In other words, to ensure that there are no gaps between tiles, neighboring tiles within neighborhood_distance cells are also considered as potential sources. Default is 5 cells.
FUN: Function to deal with overlapping values for overlapping tiles. Default is NA, which uses merge. To use mosaic, provide a compatible function
mask: If FALSE (the default), the output map will contain all cells falling within the extent of region. If TRUE, places with NA (if region is SpatRaster or Raster*) or no coverage (if region is SpatVector or Spatial*) will be assigned a value of NA.
vals: A character string or a Raster* object. Required only if the z parameter is a polygon NOT the output of the makeGrid function as the default is the character string 'location'. If not, the vals parameter should be set to the column name containing the URL or file path to the DEM for that sector.
filt: Numeric. Size of moving window to apply a low-pass filter. Default is filt = 0. Ignored unless the tiles need to be generated from the raw source files.
z_min: The minimum allowable elevation. Useful if DEM source includes ocean bathymetry as does the SRTM data from AWS. Default is z_min = NULL, but set to 0 for SRTM data. Ignored unless the tiles need to be generated from the raw source files.
dir: A filepath to the directory being used as the workspace. Default is tempdir(), but unless the analyses will only be performed a few times it is highly recommended to define a permanent workspace.
...: Additional agruments to pass to fix_z

Examples

# Generate a DEM, export it
n <- 5
dem <- expand.grid(list(x = 1:(n * 100),
                        y = 1:(n * 100))) / 100
dem <- as.data.table(dem)
dem[, z := 250 * exp(-(x - n/2)^2) + 
      250 * exp(-(y - n/2)^2)]
#>            x    y         z
#>      1: 0.01 0.01 1.0146139
#>      2: 0.02 0.01 1.0404641
#>      3: 0.03 0.01 1.0675194
#>      4: 0.04 0.01 1.0958300
#>      5: 0.05 0.01 1.1254477
#>     ---                    
#> 249996: 4.96 5.00 1.0711366
#> 249997: 4.97 5.00 1.0428260
#> 249998: 4.98 5.00 1.0157707
#> 249999: 4.99 5.00 0.9899205
#> 250000: 5.00 5.00 0.9652271
dem <- rast(dem)
ext(dem) <- c(10000, 20000, 30000, 40000)
crs(dem) <- "+proj=lcc +lat_1=48 +lat_2=33 +lon_0=-100 +datum=WGS84"

dir <- tempdir()
writeRaster(dem, paste0(dir,"/DEM.tif"),overwrite=TRUE)


# Import raster, get the grid
dem <- rast(paste0(dir,"/DEM.tif"))
grid <- makeGrid(dem = dem, nx = n, ny = n, sources = TRUE)

# Import the map for the center tile resampled to a different resolution
dem2 <- importMap('SECTOR_13', grid, res = 20)