Technical information

68 | Chapter 4 Working with Surfaces
You can define three types of breaklines.
■ Proximity breaklines: Defines breaklines using the surface points nearest
to the breakline that you draw. You do not have to snap to exact points.
■ Wall breaklines: Defines the elevations of a wall-type object on both
sides of the wall. For example, triangulation is linked to the bottom of
the wall on one side, and then begins again from the top of the wall on
the other side.
■ Standard breaklines: Defines the breaklines using the exact points or
polylines that you select.
Creating Contours to Use in Surface Generation
You can use vector contours, either polylines or contour objects, in surface
generation. However, contour data differs greatly from data taken randomly
in the field. Since contour map data is interpolated, the information may be
less accurate than direct field data. The accuracy of the final surface model
depends on the quality of both the contour map and the contour interval.
Unlike breaklines, which you create directly from within the Terrain Model
Explorer, contours (as contour objects or polylines) must already be in the
drawing in order to select them as surface data.