gdal_warp: Clip, reproject and warp raster files

In pobsteta/theia2r: An R toolbox to find, download and preprocess Sentinel-2 data

Description

The function applies gdal_translate or gdalwarp to clip, reproject and/or warp raster files. The choice of the algorythm is based on the comparison between input and output projections (gdal_translate if they are equal, gdalwarp elsewhere). If not specified, the output format of each file is the same of the corresponding source file.

Usage

gdal_warp(srcfiles, dstfiles, of = NULL, ref = NULL, mask = NULL,
  tr = NULL, t_srs = NULL, r = NULL, dstnodata = NULL,
  overwrite = FALSE, tmpdir = NA, rmtmp = TRUE, ...)

Arguments

srcfiles	A vector of input file paths (managed by GDAL).
dstfiles	A vector of corresponding output file paths.
of	The output format (use the short format name). Default is the format of every input filename.
ref	Path of the raster taken as reference: if provided, parameters regarding the output grid (alignment, resolution and extent) are taken from this raster. To set differently some of these values, specify also other values of mask and/or tr. t_srs parameter value is always ignored when ref is provided.
mask	Spatial path or object from which to take the extent of output files. If it is a polygon, this is used as masking layer; otherwise, only the bounding box is considered;. If both ref and mask are provided, this parameter will overlay the extent of the reference raster. In order to take only the grid from res and not to clip on its extent, set mask=NA. Notice that the output projection is never taken from mask.
tr	Numeric. (c(xres,yres)). set output file resolution (in target georeferenced units). If bot ref and tr are provided, tr is rounded in order to match the exact extent.
t_srs	Target spatial reference set (character). The coordinate systems that can be passed are anything supported by the OGRSpatialReference.SetFromUserInput() call, which includes EPSG PCS and GCSes (ie. EPSG:4296), PROJ.4 declarations (as above), or the name of a .prf file containing well known text.
r	Resampling_method ("near"|"bilinear"|"cubic"|"cubicspline"| "lanczos"|"average"|"mode"|"max"|"min"|"med"|"q1"|"q3").
dstnodata	Set nodata values for output bands (different values can be supplied for each band). If more than one value is supplied all values should be quoted to keep them together as a single operating system argument. New files will be initialized to this value and if possible the nodata value will be recorded in the output file. Use a value of NA to ensure that nodata is not defined. A vector with the same length of srcfiles can be supplied, in order to specify different nodata values for each input file. If this argument is not used then nodata values will be copied from the source datasets. At the moment it is not possible to set different values for different srcfiles (use multiple calls of the functions).
overwrite	Logical value: should existing output files be overwritten? (default: FALSE)
tmpdir	(optional) Path where intermediate files (maskfile) will be created. Default is a temporary directory.
rmtmp	(optional) Logical: should temporary files be removed? (Default: TRUE)
...	Additional parameters of gdalwarp or gdal_translate (different from s_srs, t_srs, te, tr, ts and of).

Note

License: GPL 3.0

Author(s)

Luigi Ranghetti, phD (2017) [e-mail]

Examples

## Not run: 
srcfiles <- c("/path/of/a/s2/file.tif",
              "/path/of/another/s2/file.tif")
crop_poly <- c("/path/of/a/polygon/vector.shp")

# Simple clip
gdal_warp(srcfiles[1],
          test0_clip <- file.path(tempdir(),"test0_clip.tif"),
          mask = get_extent(crop_poly))

# Clip and mask
gdal_warp(srcfiles,
          test0_mask <- c(file.path(tempdir(),"test0_mask.tif"),
                          tempfile()),
          mask = crop_poly)

# Warp on a reference raster
gdal_warp(srcfiles[1],
          test1 <- file.path(tempdir(),"test1.tif"),
          ref = test0_mask[1])

# Reproject all the input file
gdal_warp(srcfiles[1],
          test2 <- file.path(tempdir(),"test2.tif"),
          t_srs = "+init=epsg:32631")

# Reproject and clip on a bounding box
gdal_warp(srcfiles[1],
          test3a <- file.path(tempdir(),"test3a.tif"),
          mask = get_extent(crop_poly),
          t_srs = "+init=epsg:32631")
# Reproject and clip on polygon (masking outside)
gdal_warp(srcfiles[1],
          test3b <- file.path(tempdir(),"test3b.tif"),
          mask = crop_poly,
          t_srs = "+init=epsg:32631")
# Workaround to clip on a bounding box without
# enlarging it too much (cause of the reprojection)
gdal_warp(srcfiles[1],
          test3c <- file.path(tempdir(),"test3c.tif"),
          mask = st_cast(crop_poly,"LINESTRING"),
          t_srs = "+init=epsg:32631")

# Use a reference raster with a different projection
gdal_warp(srcfiles[1],
          test4a <- file.path(tempdir(),"test4a.tif"),
          ref = test3b)
# Use a reference raster with a different projection
# and specify a different bounding box
gdal_warp(srcfiles[1],
          test4b <- file.path(tempdir(),"test4b.tif"),
          mask = test0_clip,
          ref = test3b)
# Use a reference raster with a different projection and a mask
gdal_warp(srcfiles[1],
          test4c <- file.path(tempdir(),"test4c.tif"),
          mask = crop_poly,
          ref = test3b)

## End(Not run)

pobsteta/theia2r documentation built on May 25, 2019, 2:21 p.m.