EarthWorks Geospatial Catalog

Topographic Breaklines

Breaklines define and control surface behavior in terms of smoothness and continuity. As their name implies, breaklines are linear features. They have a significant effect in terms of describing surface behavior when incorporated in a surface model such as a triangulated irregular network (TIN). Breaklines can describe and enforce a change in the behavior of the surface. Two types of breaklines are included in this layer: hard and soft. Hard breaklines define interruptions in surface smoothness and are typically used to define streams, ridges, shorelines, building footprints, dams, and other locations of abrupt surface change. Soft breaklines are used to ensure that known "Z" (elevation) values along a linear feature (such as a roadway) are maintained in a TIN. Soft breaklines can also be used to ensure that linear features and polygon edges are maintained in the TIN surface model by enforcing the breakline as TIN edges. Soft breaklines, however, do not define interruptions in surface smoothness. The breaklines in this layer were created using Digital Terrain Model (DTM) data points collected during the production of the 1:5000 Black and White Digital Orthophoto images. They were used as input in creating TINs which were the basis for the 3-meter Elevation Contours datalayer. These breaklines are accurate to National Map Accuracy Standards (+- 1.5 meters). They are stored in the OQE library. Each coverage is named L; the layer name is BREAKLINES. The laye rin ArcSDE is named BREAKLINES_ARC.
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