Wireframe NoData Regions
NoData regions of a grid file are represented by low flat areas on a 3D wireframe map. The level of the NoData region is set to the minimum Z value for the grid file or the Elevation value on the General page, whichever is greater. For example, consider a grid file that ranges from 0 to 100 in the Z dimension. When a wireframe is created, any NoData region appears as a large flat area at the Z= 0 value, and the Elevation property value also equals 0. If the Elevation property is changed to -15, the NoData region remains and Z=0. If the Elevation value is increased to 10, the NoData region is a low flat area at Z=10.
Digital Elevation Models (DEM) may have some NoData regions along the edges of the surface. The DEM polygon contained within a 7.5-minute quadrangle consists of profiles that do not always have the same number of data points because of the variable angle between the UTM coordinate system and true north. The result is a regular, stair-stepped arrangement of the data points along the edges of the map that can translate to grid nodes assigned the NoData value along the edges of grid files produced in Surfer.