Friday, July 3, 2015

Triangulated Irregular Network (TIN)

Triangulated Irregular Network (TIN)

The Triangulation method produces a regular gridded surface through a set of data points by using an optimized Delaunay triangulation algorithm. This method is very useful for situations where the data must be honored very closely (e.g. elevation data in a digital terrain model).

Fundamentals of creating TIN surfaces
You can create a TIN surface from features, such as points, line, and polygons that contain elevation information. Use points as spot locations of elevation data. Use lines with height information to enforce natural features, such as lakes, streams, ridges, and valleys.

Creating a TIN surface from raster data
A TIN surface can also be created from other functional surfaces, such as raster or terrain datasets. You may want to convert your raster surface to a TIN to simplify the surface model for visualization & add additional features, such as streams and roads, to the surface model.

The z-tolerance is the maximum number of units by which the TIN surface may differ from the cell center heights of the input raster. A low number results in a TIN that preserves more of the detail of the raster surface. A higher number results in a more generalized representation of the surface. No. from 1 – 10.
The Z factor is used to convert z-units (for example, feet to meters).

Editing TIN Surfaces
You can add features to the TIN with the option to save it as a new TIN. For example, line feature classes that represent roadways that have been constructed or new elevation data, such as point feature classes that show mining excavation in the study area.
There are two ways to edit a TIN in ArcGIS:

Fundamentals of TIN surface analysis
Interactive 3D Analyst tools in ArcMap
TIN Conversion toolset
These conversions allow different types of analysis, show different interpretations, or extract features from TINs that you can use to enhance your analysis results or visualization in 3D.

Converting between raster and TIN formats allows you to employ the benefits of each while modeling the same surface. For example, use a TIN to model a surface if you have features, such as lines or polygons, which you want to use to enforce natural features, such as ridges or valleys, or clip a TIN to a study area. Convert this TIN to a raster using the natural neighbors interpolation option to preserve the linear features in the output raster. You'll now be able to use spatial operators on the raster that may not have been available for the TIN. In addition, the TIN-to-raster conversion is a smoothing process, so contours you generate on the raster are smoother than they would be as a TIN.

Displaying TIN surfaces
The internal structure of a TIN contains nodes, edges, and faces, which can independently display different surface characteristics in either ArcMap or ArcScene. These surface characteristics include slope, aspect, elevation, and contours.

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