What are abrupt changes in the shape of a surface called in TINs?

In Triangulated Irregular Networks (TINs), abrupt changes in the shape of a surface are referred to as breaklines. Breaklines are crucial for accurately representing features such as ridges, valleys, or fence lines because they indicate places where the surface exhibits a significant change in slope or direction. When constructing a TIN, incorporating breaklines ensures that these critical features are maintained, allowing for a more accurate representation of the terrain.

Breaklines serve as constraints that the triangulation process respects, resulting in a surface model that aligns closely with the physical reality of the landscape. This is especially important in high-resolution modeling where precision is needed for analysis or visualization. The other options—contours, nodes, and segments—while related to TINs, do not specifically denote abrupt changes in the surface's shape. Contours represent elevation lines, nodes are points where the triangles meet, and segments are the edges of the triangles, none of which capture the essence of abrupt changes effectively like breaklines do.