Digital Elevation Models II TIN Data Structures

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Digital Elevation Models IITIN Data Structures

• RNR/GEOG 420-520
• Winter -- 2000

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Triangulated Irregular Network

• Triangulated Irregular Networks (TIN)
• Computed from irregularly spaced points with x,y
  and z values

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Triangular Irregular Network

• Triangulated Irregular Networks (TIN)
• Based on a Delauney triangulation scheme
• Data Points are connected to form a network of
  adjacent non-overlapping triangles

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TIN Creation in ARC/INFO Features

• Mass Points
• Breaklines
• Linear or Polygonal
• Hard breaklines
• Soft breaklines
• Exclusion Polygons
• Replace
• Erase
• Clip

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TIN Creation (contd.)

• ARCs CREATETIN, uses a variety of data sources
• These sources can be combined in a number of ways
  to create the TIN

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Why You Might Prefer a TIN

• GRID
• Data redundancy in areas of uniform terrain
• Inability to adapt to areas of differing relief
  complexity
• Exaggerated emphasis along the axis of the grid

• TIN
• Non-redundant data
• Allows extra data in complex areas and less data
  in non-complex areas
• The ability to use natural features as
  break-lines
• The triangles are cute

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TINs and Surface Analysis

• Interpolation of z values
• Generation of contour lines and contour bands
• Calculation of slope and aspect
• Calculation of surface area and surface length
• Calculation of volume and cut and fill analysis
• Determination of the intervisibility between two
  points
• Analysis of what is visible from one or more
  observation points
• Assessment of the visual quality of each region
  in a viewshed
• Profiles across single or multiple surfaces
• Hillshading based on a specified illumination
  source location

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What TINs are Really Good At

• Tins are really good at 3D display of real world
  surfaces
• Shaded models from things such as a raster DEM
  can be draped on top of an underlying TIN
  structure

9
What TINs are Really Good At

• Tins are really good at 3D display of real world
  surfaces
• Shaded models from things such as a raster DEM
  can be draped on top of an underlying TIN
  structure