ET Surface is a set of tools for ArcGIS that enable the users to create surfaces and perform surface analysis without the need of 3D or Spatial Analyst extensions. The only requirement is an ArcGIS license (ArcView, ArcEditor or ArcInfo).
ET Surface 2.0 introduces ET TerrainViewer which allows 3D visualization of surfaces (PolygonZ TINs and Rasters) as well as features stored in shapefiles.
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.
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