vapour_raster_gcp: Raster ground control points

In vapour: Access to the 'Geospatial Data Abstraction Library' ('GDAL')

Raster ground control points

Description

Return any ground control points for a raster data set, if they exist.

Usage

vapour_raster_gcp(x, ...)

Arguments

x	data source string (i.e. file name or URL or database connection string)
...	ignored currently

Details

Pixel and Line coordinates do not correspond to cells in the underlying raster grid, they refer to the index space of that array in 0, ncols and 0, nrows. They are usually a subsample of the grid and may not align with the grid spacing itself (though they often do in satellite remote sensing products).

The coordinate system of the GCPs is currently not read.

Value

list with

• Pixel the pixel coordinate

• Line the line coordinate

• X the X coordinate of the GCP

• Y the Y coordinate of the GCP

• Z the Z coordinate of the GCP (usually zero)

Examples

## this file has no ground control points
## they are rare, and tend to be in large files
f <- system.file("extdata", "sst.tif", package = "vapour")
vapour_raster_gcp(f)

## a very made-up example with no real use
f1 <- system.file("extdata/gcps", "volcano_gcp.tif", package = "vapour")
vapour_raster_gcp(f1)

vapour documentation built on June 22, 2024, 10:01 a.m.