gdal_contour(1) General Commands Manual gdal_contour(1)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] [-f <formatname>] [-i <interval>]
[-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.
-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
GDAL Tue Sep 18 2012 gdal_contour(1)
Check Out this Related Man Page
GLUNEXTCONTOUR(3G)GLUNEXTCONTOUR(3G)NAME
gluNextContour - mark the beginning of another contour
C SPECIFICATION
void gluNextContour( GLUtesselator* tess,
GLenum type )
PARAMETERS
tess Specifies the tessellation object (created with gluNewTess).
type Specifies the type of the contour being defined. Valid values are GLU_EXTERIOR, GLU_INTERIOR, GLU_UNKNOWN, GLU_CCW, and GLU_CW.
DESCRIPTION
gluNextContour is used in describing polygons with multiple contours. After the first contour has been described through a series of
gluTessVertex calls, a gluNextContour call indicates that the previous contour is complete and that the next contour is about to begin.
Another series of gluTessVertex calls is then used to describe the new contour. This process can be repeated until all contours have been
described.
type defines what type of contour follows. The legal contour types are as follows:
GLU_EXTERIOR An exterior contour defines an exterior boundary of the polygon.
GLU_INTERIOR An interior contour defines an interior boundary of the polygon (such as a hole).
GLU_UNKNOWN An unknown contour is analyzed by the library to determine if it is interior or exterior.
GLU_CCW,
GLU_CW The first GLU_CCW or GLU_CW contour defined is considered to be exterior. All other contours are considered to be exte-
rior if they are oriented in the same direction (clockwise or counterclockwise) as the first contour, and interior if
they are not.
If one contour is of type GLU_CCW or GLU_CW, then all contours must be of the same type (if they are not, then all GLU_CCW and GLU_CW con-
tours will be changed to GLU_UNKNOWN).
Note that there is no real difference between the GLU_CCW and GLU_CW contour types.
Before the first contour is described, gluNextContour can be called to define the type of the first contour. If gluNextContour is not
called before the first contour, then the first contour is marked GLU_EXTERIOR.
This command is obsolete and is provided for backward compatibility only. Calls to gluNextContour are mapped to gluTessEndContour followed
by gluTessBeginContour.
EXAMPLE
A quadrilateral with a triangular hole in it can be described as follows:
gluBeginPolygon(tobj);
gluTessVertex(tobj, v1, v1);
gluTessVertex(tobj, v2, v2);
gluTessVertex(tobj, v3, v3);
gluTessVertex(tobj, v4, v4); gluNextContour(tobj, GLU_INTERIOR);
gluTessVertex(tobj, v5, v5);
gluTessVertex(tobj, v6, v6);
gluTessVertex(tobj, v7, v7); gluEndPolygon(tobj);
SEE ALSO
gluBeginPolygon, gluNewTess, gluTessCallback, gluTessVertex, gluTessBeginContour
GLUNEXTCONTOUR(3G)