NAME

       gdal_contour - gdal_contour builds vector contour lines from a raster elevation model

SYNOPSIS

       Usage: gdal_contour [-b <band>] [-a <attribute_name>] [-3d] [-inodata]
                           [-snodata n] [-i <interval>]
                           [-f <formatname>] [[-dsco NAME=VALUE] ...] [[-lco NAME=VALUE] ...]
                           [-off <offset>] [-fl <level> <level>...]
                           [-nln <outlayername>]
                           <src_filename> <dst_filename>

DESCRIPTION

       This program generates a vector contour file from the input raster elevation model (DEM).

       Starting from version 1.7 the contour line-strings will be oriented consistently. The high
       side will be on the right, i.e. a line string goes clockwise around a top.

       -b band:
           picks a particular band to get the DEM from. Defaults to band 1.

       -a name:
           provides a name for the attribute in which to put the elevation. If not provided no
           elevation attribute is attached.

       -3d:
           Force production of 3D vectors instead of 2D. Includes elevation at every vertex.

       -inodata:
           Ignore any nodata value implied in the dataset - treat all values as valid.

       -snodata value:
           Input pixel value to treat as 'nodata'.

       -f format:
           create output in a particular format, default is shapefiles.

       -dsco NAME=VALUE:
           Dataset creation option (format specific)

       -lco NAME=VALUE:
           Layer creation option (format specific)

       -i interval:
           elevation interval between contours.

       -off offset:
           Offset from zero relative to which to interpret intervals.

       -fl level:
           Name one or more 'fixed levels' to extract.

       -nln outlayername:
           Provide a name for the output vector layer. Defaults to 'contour'.

EXAMPLE

       This would create 10meter contours from the DEM data in dem.tif and produce a shapefile in
       contour.shp/shx/dbf with the contour elevations in the 'elev' attribute.

       gdal_contour -a elev dem.tif contour.shp -i 10.0

AUTHORS

       Frank Warmerdam warmerdam@pobox.com, Silke Reimer silke@intevation.de