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Apply geotransform (raster column/row to geospatial x/y)

Source: R/gdal_helpers.R
apply_geotransform.Rd

apply_geotransform() applies geotransform coefficients to raster coordinates in pixel/line space (column/row), converting into georeferenced (x/y) coordinates. Wrapper of GDALApplyGeoTransform() in the GDAL API, operating on matrix input.

Usage

apply_geotransform(col_row, gt)

Arguments

col_row

Numeric matrix of raster column/row (pixel/line) coordinates (or two-column data frame that will be coerced to numeric matrix).

gt

Either a numeric vector of length six containing the affine geotransform for the raster, or an object of class GDALRaster from which the geotransform will be obtained.

Value

Numeric matrix of geospatial x/y coordinates.

Note

Bounds checking on the input coordinates is done if gt is obtained from an object of class GDALRaster. See Note for get_pixel_line().

See also

GDALRaster$getGeoTransform(), get_pixel_line()

Examples

raster_file <- system.file("extdata/storm_lake.lcp", package="gdalraster")
ds <- new(GDALRaster, raster_file)

# compute some raster coordinates in column/row space
set.seed(42)
col_coords <- runif(10, min = 0, max = ds$getRasterXSize() - 0.00001)
row_coords <- runif(10, min = 0, max = ds$getRasterYSize() - 0.00001)
col_row <- cbind(col_coords, row_coords)

# convert to geospatial x/y coordinates
gt <- ds$getGeoTransform()
apply_geotransform(col_row, gt)
#>           [,1]    [,2]
#>  [1,] 327400.6 5103613
#>  [2,] 327496.1 5102774
#>  [3,] 324703.6 5102082
#>  [4,] 327038.7 5104262
#>  [5,] 326229.2 5103598
#>  [6,] 325703.0 5102065
#>  [7,] 326636.0 5101942
#>  [8,] 324053.8 5104705
#>  [9,] 326294.6 5103557
#> [10,] 326500.8 5103283

# or, using the class method
ds$apply_geotransform(col_row)
#>           [,1]    [,2]
#>  [1,] 327400.6 5103613
#>  [2,] 327496.1 5102774
#>  [3,] 324703.6 5102082
#>  [4,] 327038.7 5104262
#>  [5,] 326229.2 5103598
#>  [6,] 325703.0 5102065
#>  [7,] 326636.0 5101942
#>  [8,] 324053.8 5104705
#>  [9,] 326294.6 5103557
#> [10,] 326500.8 5103283

# bounds checking
col_row <- rbind(col_row, c(ds$getRasterXSize(), ds$getRasterYSize()))
ds$apply_geotransform(col_row)
#> Warning: 1 coordinates(s) were outside the raster extent, NA returned
#>           [,1]    [,2]
#>  [1,] 327400.6 5103613
#>  [2,] 327496.1 5102774
#>  [3,] 324703.6 5102082
#>  [4,] 327038.7 5104262
#>  [5,] 326229.2 5103598
#>  [6,] 325703.0 5102065
#>  [7,] 326636.0 5101942
#>  [8,] 324053.8 5104705
#>  [9,] 326294.6 5103557
#> [10,] 326500.8 5103283
#> [11,]       NA      NA

ds$close()