General raster read and convert — gdal_raster

The warper is used to convert source/s to an output file or to data in memory.

gdal_raster_data(
  dsn,
  target_crs = NULL,
  target_dim = NULL,
  target_ext = NULL,
  target_res = NULL,
  resample = "near",
  bands = 1L,
  band_output_type = NULL,
  options = character(),
  include_meta = TRUE
)

gdal_raster_dsn(
  dsn,
  target_crs = NULL,
  target_dim = NULL,
  target_ext = NULL,
  target_res = NULL,
  resample = "near",
  bands = NULL,
  band_output_type = NULL,
  options = character(),
  out_dsn = tempfile(fileext = ".tif"),
  include_meta = TRUE
)

gdal_raster_image(
  dsn,
  target_crs = NULL,
  target_dim = NULL,
  target_ext = NULL,
  target_res = NULL,
  resample = "near",
  bands = NULL,
  band_output_type = NULL,
  options = character(),
  include_meta = TRUE
)

gdal_raster_nara(
  dsn,
  target_crs = NULL,
  target_dim = NULL,
  target_ext = NULL,
  target_res = NULL,
  resample = "near",
  bands = NULL,
  band_output_type = NULL,
  options = character(),
  include_meta = TRUE
)

Arguments

dsn: data sources, files, urls, db strings, vrt, etc
target_crs: projection of the target grid
target_dim: dimension of the target grid
target_ext: extent of the target grid
target_res: resolution of the target grid
resample: resampling algorithm used
bands: band or bands to include, default is first band only (use NULL or a value less that one to obtain all bands)
band_output_type: specify the band type, see vapour_read_raster
options: general options passed to gdal warper
include_meta: metadata is attached, turn off by setting this to FALSE
out_dsn: file name for output "_dsn"

Value

pixel values in a list vector per band, or a list of file paths

Details

Two functions 'gdal_raster_data' and 'gdal_raster_dsn' act like the gdalwarp command line tool, a convenience third function 'gdal_raster_image()' works especially for image data.

Examples

dsn <- system.file("extdata/sst.tif", package = "vapour")
## do nothing, get native
X <- gdal_raster_data(dsn)

## set resolution (or dimension, extent, crs, or combination thereof - GDAL 
## will report/resolve incompatible opts)
X1 <- gdal_raster_data(dsn,  target_res = 1)

## add a cutline, and cut to it using gdal warp args

if (interactive()) {
 cutline <- tempfile(fileext = ".csv")
 wkt <- "POLYGON ((142 -41, 149 -41, 146 -58, 142 -41))"
 write.csv(data.frame(id = 1, WKT = wkt), cutline, row.names = FALSE)
 X1c <- gdal_raster_data(dsn,  target_res = .5, 
     options = c("-cutline",cutline, "-crop_to_cutline"))
 file.remove(cutline)
}

## warp whole grid to given res
X2 <- gdal_raster_data(dsn,  target_res = 25000, target_crs = "EPSG:32755")

## specify exactly (as per vapour originally)
X3 <- gdal_raster_data(dsn,  target_ext = c(-1, 1, -1, 1) * 8e6, 
 target_dim = c(512, 678), target_crs = "+proj=stere +lon_0=147 +lat_0=-90")
 
X4 <- gdal_raster_dsn(dsn, out_dsn = tempfile(fileext = ".tif"))