preproc() crops an input grid to a specified extent with a polygon or SpatExtent,
reprojects the grid to a specified coordinate system, and converts the data from integer
to floating point using an offset and a scale factor.
Usage
preproc(
grd,
drivers = NULL,
outline = NULL,
coords = NULL,
add_offset = 0,
scale_factor = 1
)Arguments
- grd
filename (character) or SpatRaster of the raster to be processed, in one of GDAL's raster drivers.
- drivers
character. GDAL drivers to consider
- outline
filename (character) of the shapefile containing the outline of the area of interest, in
.shpformat, or SpatExtent giving a vector of length four (xmin, xmax, ymin, ymax).- coords
filename (character) or SpatRaster of the raster with the coordinate system definition. Alternatively, a coordinate reference system (CRS) description can be provided. In this case, the CRS can be described using the PROJ-string (e.g., "+proj=longlat +datum=WGS84") or the WKT format (e.g., "EPSG:4326").
- add_offset
band-specific offset added to each grid value. Defaults to zero.
- scale_factor
band-specific scale factor applied to each grid value. Defaults to one.
See also
terra::rast(), terra::ext(), and terra::project() which this function wraps.
Examples
# uncorrected grid
f <- system.file("extdata/athabasca_B03_20200911.tif", package = "SatRbedo")
preproc(grd = f)
#> class : SpatRaster
#> size : 207, 216, 1 (nrow, ncol, nlyr)
#> resolution : 30, 30 (x, y)
#> extent : 477840, 484320, 5778300, 5784510 (xmin, xmax, ymin, ymax)
#> coord. ref. : WGS 84 / UTM zone 11N (EPSG:32611)
#> source(s) : memory
#> varname : athabasca_B03_20200911
#> name : Green
#> min value : -0.0829
#> max value : 1.3276
# crop grid
g <- system.file("extdata/athabasca_B03_20200911.tif", package = "SatRbedo")
v <- system.file("extdata/athabasca_outline.shp", package = "SatRbedo")
preproc(grd = g, outline = v)
#> class : SpatRaster
#> size : 205, 214, 1 (nrow, ncol, nlyr)
#> resolution : 30, 30 (x, y)
#> extent : 477870, 484290, 5778330, 5784480 (xmin, xmax, ymin, ymax)
#> coord. ref. : WGS 84 / UTM zone 11N (EPSG:32611)
#> source(s) : memory
#> varname : athabasca_B03_20200911
#> name : Green
#> min value : -0.0323
#> max value : 1.2973
# crop and reproject grid
g <- system.file("extdata/athabasca_B03_20200911.tif", package = "SatRbedo")
v <- system.file("extdata/athabasca_outline.shp", package = "SatRbedo")
preproc(grd = g, outline = v, coords = "+proj=longlat +datum=WGS84")
#> class : SpatRaster
#> size : 151, 256, 1 (nrow, ncol, nlyr)
#> resolution : 0.0003683312, 0.0003683312 (x, y)
#> extent : -117.3239, -117.2296, 52.15492, 52.21054 (xmin, xmax, ymin, ymax)
#> coord. ref. : +proj=longlat +datum=WGS84 +no_defs
#> source(s) : memory
#> name : Green
#> min value : -0.03039604
#> max value : 1.27545702
preproc(grd = g, outline = v, coords = "EPSG:4326")
#> class : SpatRaster
#> size : 151, 256, 1 (nrow, ncol, nlyr)
#> resolution : 0.0003683312, 0.0003683312 (x, y)
#> extent : -117.3239, -117.2296, 52.15492, 52.21054 (xmin, xmax, ymin, ymax)
#> coord. ref. : lon/lat WGS 84 (EPSG:4326)
#> source(s) : memory
#> name : Green
#> min value : -0.03039604
#> max value : 1.27545702
# Transform grid values
library(terra)
g <- system.file("extdata/athabasca_B03_20200911.tif", package = "SatRbedo")
orig <- preproc(grd = g)
minmax(orig)
#> Green
#> min -0.0829
#> max 1.3276
new <- preproc(grd = g, add_offset = 5, scale_factor = 10)
minmax(new)
#> Green
#> min 4.171
#> max 18.276