.TH "gdal_contour" 1 "28 Jun 2006" "GDAL" \" -*- nroff -*-
.ad l
.nh
.SH NAME
gdal_contour \- gdal_contour
builds vector contour lines from a raster elevation model
.SH "SYNOPSIS"
.PP
.PP
.PP
.nf
Usage: gdal_contour [-b <band>] [-a <attribute_name>] [-3d] [-inodata]
                    [-snodata n] [-f <formatname>] [-i <interval>]
                    [-off <offset>] [-fl <level> <level>...]
                    <src_filename> <dst_filename> 
.fi
.PP
.SH "DESCRIPTION"
.PP
This program generates a vector contour file from the input raster elevation model (DEM).
.PP
.IP "\fB\fB-s_srs\fP \fIsrs def\fP:\fP" 1c
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
.PP
.IP "\fB\fB-b\fP \fIband\fP:\fP" 1c
picks a particular band to get the DEM from. Defaults to band 1.
.PP
.IP "\fB\fB-a\fP \fIname\fP:\fP" 1c
provides a name for the attribute in which to put the elevation. If not provided no elevation attribute is attached.  
.IP "\fB\fB-3d\fP: \fP" 1c
Force production of 3D vectors instead of 2D. Includes elevation at every vertex.
.PP
.IP "\fB\fB-inodata\fP: \fP" 1c
Ignore any nodata value implied in the dataset - treat all values as valid.
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.IP "\fB\fB-snodata\fP \fIvalue\fP:\fP" 1c
Input pixel value to treat as 'nodata'. 
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.IP "\fB\fB-f\fP \fIformat\fP: \fP" 1c
create output in a particular format, default is shapefiles.
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.IP "\fB\fB-i\fP \fIinterval\fP:\fP" 1c
elevation interval between contours.
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.IP "\fB\fB-off\fP \fIoffset\fP:\fP" 1c
Offset from zero relative to which to interpret intervals.
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.IP "\fB\fB-fl\fP \fIlevel\fP: \fP" 1c
Name one or more 'fixed levels' to extract. 
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.SH "EXAMPLE"
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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.
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.PP
.nf
gdal_contour -a elev dem.tif contour.shp 10.0
.fi
.PP
.SH "AUTHORS"
.PP
Frank Warmerdam <warmerdam@pobox.com>, Silke Reimer <silke@intevation.de>