Replace polygons

Replace polygons create a flat area on a TIN surface. They are used to model formations like building foundations, terraces, and other graded areas.

Top: Simple mass point triangulation does not adequately model the creek. Bottom: The creek is modeled with a replace polygon.

A replace polygon stores a single elevation value as an attribute. When you add the polygon, the TIN is retriangulated so that the surface area covered by the polygon has this value.

Top: The blue polygon (a creek) will be added to the TIN as a replace polygon. This is necessary because the default triangulation wrongly represents the area as sloped. Bottom: The replace polygon sides become triangle edges. The area within the replace polygon has a constant elevation (no slope).