inv_geotransform {gdalraster}

Invert geotransform

Description

inv_geotransform() inverts a vector of geotransform coefficients. This converts the equation from being:
raster pixel/line (column/row) -> geospatial x/y coordinate
to:
geospatial x/y coordinate -> raster pixel/line (column/row)

Usage

inv_geotransform(gt)

Arguments

gt

Numeric vector of length six containing the geotransform to invert.

Value

Numeric vector of length six containing the inverted geotransform. The output vector will contain NAs if the input geotransform is uninvertable.

See Also

GDALRaster$getGeoTransform(), get_pixel_line()

Examples

elev_file <- system.file("extdata/storml_elev.tif", package="gdalraster")
ds <- new(GDALRaster, elev_file)
invgt <- ds$getGeoTransform() |> inv_geotransform()
ds$close()

ptX = 324181.7
ptY = 5103901.4

## for a point x, y in the spatial reference system of elev_file
## raster pixel (column number):
pixel <- floor(invgt[1] +
               invgt[2] * ptX +
               invgt[3] * ptY)

## raster line (row number):
line <- floor(invgt[4] +
              invgt[5] * ptX +
              invgt[6] * ptY)

## get_pixel_line() applies this conversion