Types of Surfaces

The functions and tools of ET Surface can be used in on 2 types of surfaces - Rasters and TINs

Rasters represent the surface using a matrix of uniformly sized square areas. Each square, which may be referred to as a cell or pixel stores a single value that represents what the surface represent. The most common case of the value of a cell is elevation of a terrain, but it can be many other things (temperature, rainfall, etc.). Each cell of a georeferenced raster represents a physical cell in the space. The size of the cells define the resolution of the raster - smaller cells - better resolution - larger size of the raster.

The TIN model represents a surface as a set of contiguous, non-overlapping triangles. Within each triangle the surface is represented by a plane. The triangles are made from a set of points called mass points.

See TIN Notes for more information about TINs

ET Surface can generate only a TIN surface, but most of the functionality can be used with both Raster and TIN surfaces.

Raster formats that can be used:

• ESRI Grid
• ERDAS Imagine images (.img)
• Tagged Image File Format (TIFF) image (.tif)

TIN Formats that can be used:

• ESRI TIN - proprietary format. Surfaces created by 3D Analyst or Arc/Info TIN module or ET Surface version 4.0.
• PolygonZ TIN - A TIN Surface stored in a PolygonZ dataset (Shapefile, Personal or File Geodatabase). Surfaces created by ET GeoWizards and ET Surface.

A list of the functions of ET Surface and surfaces on which they can be used