gdal_contour {gdalUtils} | R Documentation |
R wrapper for gdal_contour: builds vector contour lines from a raster elevation model
gdal_contour( src_filename, dst_filename, b, a, threeD, inodata, snodata, i, f = "ESRI Shapefile", dsco, lco, off, fl, nln, output_Vector = FALSE, config, ignore.full_scan = TRUE, verbose = FALSE )
src_filename |
Character. Any OGR supported readable datasource. |
dst_filename |
Character. The OGR supported output file. |
b |
Numeric. Picks a particular band to get the DEM from. Defaults to band 1. |
a |
Character. Provides a name for the attribute in which to put the elevation. If not provided no elevation attribute is attached. |
threeD |
Logical. (GDAL parameter '3d') Force production of 3D vectors instead of 2D. Includes elevation at every vertex. |
inodata |
Logical. Ignore any nodata value implied in the dataset - treat all values as valid. |
snodata |
Numeric. Input pixel value to treat as "nodata". |
i |
Numeric. Elevation interval between contours. |
f |
Character. Create output in a particular format, default is "ESRI Shapefiles". |
dsco |
Character. Dataset creation option (format specific). Follows "NAME=VALUE" format. |
lco |
Character. Layer creation option (format specific). Follows "NAME=VALUE" format. |
off |
Numeric. Offset from zero relative to which to interpret intervals. |
fl |
Character. Name one or more "fixed levels" to extract. |
nln |
Character. Provide a name for the output vector layer. Defaults to "contour". |
output_Vector |
Logical. Return output dst_filename as a Spatial* object. Currently only works with f="ESRI Shapefile". |
config |
Character. Sets runtime configuration options for GDAL. See https://trac.osgeo.org/gdal/wiki/ConfigOptions for more information. |
ignore.full_scan |
Logical. If FALSE, perform a brute-force scan if other installs are not found. Default is TRUE. |
verbose |
Logical. Enable verbose execution? Default is FALSE. |
This is an R wrapper for the 'gdal_contour' function that is part of the Geospatial Data Abstraction Library (GDAL). It follows the parameter naming conventions of the original function, with some modifications to allow for more R-like parameters. For all parameters, the user can use a single character string following, precisely, the gdal_contour format (http://www.gdal.org/gdal_contour.html), or, in some cases, can use R vectors to achieve the same end.
This function assumes the user has a working GDAL on their system. If the "gdalUtils_gdalPath" option has been set (usually by gdal_setInstallation), the GDAL found in that path will be used. If nothing is found, gdal_setInstallation will be executed to attempt to find a working GDAL that has the right drivers as specified with the "of" (output format) parameter.
The user can choose to (optionally) return a RasterBrick of the output file (assuming raster/rgdal supports the particular output format).
output vector filename or SpatialLinesDataFrame object.
Jonathan A. Greenberg (gdalUtils@estarcion.net) (wrapper) and Frank Warmerdam (GDAL lead developer).
http://www.gdal.org/gdal_contour.html
# We'll pre-check to make sure there is a valid GDAL install # and that raster and rgdal are also installed. # Note this isn't strictly neccessary, as executing the function will # force a search for a valid GDAL install. gdal_setInstallation() valid_install <- !is.null(getOption("gdalUtils_gdalPath")) if(require(raster) && require(rgdal) && valid_install) { # Example from the original gdal_contour documentation: # gdal_contour -a elev dem.tif contour.shp -i 10.0 # Choose a DEM: input_dem <- system.file("external/tahoe_lidar_bareearth.tif", package="gdalUtils") # Setup an output filename (shapefile): output_shapefile <- paste(tempfile(),".shp",sep="") contour_output <- gdal_contour(src_filename=input_dem,dst_filename=output_shapefile, a="Elevation",i=5.,output_Vector=TRUE) # Plot the contours using spplot: spplot(contour_output["Elevation"],contour=TRUE) }