The Create Contours (from Terrain Grid) command allows the user to generate equally spaced contour lines from any loaded elevation grid data. Choose this option from the Analysis Menu, or the Analysis Toolbar button.
When selected, the command displays the Contour Generation Options dialog (pictured below) which allows the user to set up the contour generation process.
The Contour Generation Options panel
(displayed above) allows the user to set the contour interval and units
as well as the grid spacing to use when generating the contours. The Elevation Range settings can be
used to restrict which contour lines are generated (by default all loaded
elevation values are considered). In addition, options are available to
generate height area features in addition to contour lines as well as
spot elevations at the highest and lowest points in the area over which
the contours are generated.
The Resampling drop-down allows
the user to control how terrain layers are sampled during contour generation.
The Smooth Contour Lines option
controls whether or not extra vertices are added along generated line
and area features to improve their appearance.
To generate a large number of contour lines over a large area, the option to export the contours directly to a package file can be used in addition to the Gridding tab options to export contours directly to package files, sometimes by passing memory limitations. Note that the contour lines will be generated so that the higher elevations are to the left of the contour line.
Create Contours Where Elevations Pass
Down to Contour Value Rather Than as They Go Down From One option
is an advanced option to change how the contouring works in flat areas.
If this option is checked, contours generated where the terrain
surface arrives at a contour height from higher terrain, rather than where
it departs a contour height for lower terrain. With a flat plain exactly
at a contour height, the result will be a contour at the base of the hill
where it starts up, rather than at the top where it starts down. This
is most useful when using with datasets that include water (like the ocean)
and want to get a shoreline contour generated where the terrain leaves
the flat surface of the water.
Use Discard Closed Contour Lines Shorter than X meters to specify a minimum length for any closed contours. Any closed (i.e. complete loop) contours less than the specified length will be marked as deleted.
The Simplification panel (displayed below) allows the user to set up the threshold at which points that don't contribute much to the shape of the generated contour are removed in order to generate lines with less vertices.
The Gridding panel allows the
user o break up the contour generation into smaller pieces, which can
sometimes help reduce memory requirements when generating a very large
amount of contour lines.
The Export Bounds panel allows
the user to set up the portion of the loaded elevation grid data they
wish to consider when generating the contours.
The Generate Contours (from TIN
Areas) command allows the user to generate contour lines from any loaded
TIN Area (Triangulated Irregular Network).
*Note that when generating contours from a TIN Area not all Contour Generation Options will be available.