This program generates a vector contour file from the input raster elevation model (DEM).
-s_srssrs def:
source spatial reference set. The coordinate systems that can be passed are anything supported by the OGRSpatialReference.SetFromUserInput() call, which includes EPSG PCS and GCSes (ie. EPSG:4296), PROJ.4 declarations (as above), or the name of a .prf file containing well known text. </dl
-bband:
picks a particular band to get the DEM from. Defaults to band 1.
-aname:
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.
-snodatavalue:
Input pixel value to treat as "nodata".
-fformat:
create output in a particular format, default is shapefiles.
-iinterval:
elevation interval between contours.
-offoffset:
Offset from zero relative to which to interpret intervals.
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.