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					Technical Workshops




      3D Analyst
Surface Analysis
   Clayton Crawford
    Raghav Vemula
3D Geoprocessing Tools


  •   Surface Tools
       -   Creation
       -   Editing
       -   Analysis
  •   Data Conversion Tools
       -   Between surface models
       -   From surface models to
           features
Surface Creation


  •   Raster
       -   Import (core toolset)
       -   Interpolation
  •   TIN
       -   Triangulation
  •   Terrain Dataset
       -   TIN based
Raster Interpolation


  •   Variety of interpolants
       -   TopoToRaster, Natural Neighbors, IDW, Spline, Kriging,
           Trend, TIN/Terrain to Raster (Conversion toolset)
  •   Select one to use based on:
       -   Application requirements
       -   Characteristics of available data
       -   Ability of interpolant to handle above
Topo To Raster


  •   Strengths
       -   Handles contour data on input
       -   Hydrologically sound output
  •   Supported input data types
       -   Contours with height attribute
       -   2D points with attribute
       -   2D polylines (rivers)
Spline


  •   Strengths
       -   Smooth
       -   Infers trends
  •   Supported input data types
       -   Points (2D with attribute, 3D)
       -   Barriers
Inverse Distance Weighted (IDW)


  •   Strengths
       -   Fast
       -   Interpolated z range within range of data
  •   Supported input data types
       -   Points (2D with attribute, 3D)
       -   Barriers
Natural Neighbors


  •   Strengths
       -   Conservatively smooth
       -   Interpolated z range within range of data
       -   Smart selection of samples
  •   Supported input data types
       -   Points (2D with attribute, 3D)
       -   Note: also supported by TIN to Raster
Kriging


  •   Strengths
       -   Probabilistic
       -   Well behaved with sparse data
       -   Options to tailor results based on input data
           characteristics
       -   Statistical assessment of estimates
  •   Supported input data types
       -   Points (2D with attribute, 3D)
TIN/Terrain Dataset


  •   Strengths
       -   Inputs incorporated directly into model
       -   Precise, honors input samples exactly
       -   Adapts to variability of terrain
  •   Supported input data types
       -   Points, lines, and polygons (2D with attribute, 3D)
       -   3D breaklines
TIN/Terrain and Surface Feature Types


  •   Mass, break, clip, erase, replace
  •   Hard/soft edge enforcement
Mass Points
Replace Polygons
Erase Polygons
    Clip Polygons




Tip: Don’t have a clip polygon? Try DelineateTINDataArea
Conversion Between TINs/Terrains and Rasters


  •   Raster to TIN
       -   Z tolerance
       -   OK to use as ‘smart’ generalization for visualization or
           when ancillary data is available to improve surface
  •   TIN To Raster / Terrain To Raster
       -   Linear and natural neighbors interpolation options
       -   Benefit over Natural Neighbors tool offered in Raster
           Interpolation toolbox is support of constraints like
           breaklines and clip polygons
  •   TIN to terrain dataset
       -   Use the tools available to convert TINs to features
            -   TIN Node, TIN Line, TIN Domain
       -   Build terrain from resulting features
Radial Search




     Even distribution   Variable distribution
Triangle Search
Natural Neighbors Search
Profile Comparison Between Interpolants

       1400
       1200
       1000
        800
        600
        400
        200
          0
        -200
        -400
        -600

                TIN Linear       TopoRaster             Spline
                  Data samples omitted in these areas
TIN/Terrain to Raster with Natural Neighbors


                                         ‘hard’ edge




  Linear              Natural              Natural
                     Neighbors           Neighbors
                                        (break edge)
Breakline Enforcement
Demo
Surface Analysis

 •   Derivatives                      •   Visibility
      -   Slope                            -   Viewshed
      -   Aspect                           -   Line of Sight
      -   Hillshade



 •   Feature Interpolation            •   Volume
      -   Interpolate Shape                -   Surface Volume
      -   Interpolate Poly To Patch        -   Cut Fill
      -   Surface Length                   -   Surface Difference
      -   Surface Spot                     -   Polygon Volume
      -   Contour                          -   Extrude Between
Slope: steepness




Aspect: direction of steepest slope




Hillshade: steepness and direction
relative to light source
Derivative Calculation

 •   Raster based
      -   Local functions, 3x3 roving windows
      -   Plane fitted to this ‘neighborhood’


 •   TIN based
      -   Each triangle defines a plane unambiguously
3x3 Roving Windows




   Note: Hillshade will not estimate values for boundary cells
Interpolation

 •   Feature interpolation
      -   Raster
          -   Bilinear
          -   Sample distance
      -   TIN
          -   Linear
          -   Natural Neighbors
          -   ‘Natural’ densification


 •   Contouring
      -   Raster and TIN based methods
          -   Linear threading through triangles
Cell vs. Surface Data Area
  Raster
  image                                                Surface
 boundary                                              domain




        Interpolation zone is ½ cell in from image boundary
Cell vs. Surface Data Area




                      Raster
                     Hillshade
                     domain
                      extent
                      extent
Raster Profile Sampling
TIN Profile Sampling
Visibility

 •   Line Of Sight (LOS)
      -   Inputs are 2D or 3D lines
      -   Only 1st and last vertices used as observer and target
          points
      -   Raster and TIN implementations


 •   Viewshed
      -   Frequency and Observers options/tools
      -   Raster algorithm


 •   Earth curvature
Line of Sight

               231
               206
   Elevation




                                                            Target
               181




                         Observer
               156




                     0              75   150          225   300      345

                                           Distance
Line of Sight




                                                     Offset




  When offset, the target can be visible even though the profile
  on the surface at that position is not.
Line of Sight

               231

                              Obstruction Point
               206
   Elevation
               181
               156




                     0   75              150            225   300   345

                                             Distance

  When a target isn’t visible, its obstruction point always
  occurs along a visible portion of the profile.
Curvature and Refraction

 •   Adjustment made to consider effects of earth
     curvature and atmospheric refraction on result
      -   Curvature reduces visibility over distance
      -   Refraction increases visibility


 •   More significant impact over longer distances


 •   Curvature, in effect, decreases elevation 7.85 meters
     per 10km distance.


 •   Use of default refraction brings that back to 6.83
     meters
Volumetrics

 •   CutFill
      -   Raster/cell based


 •   SurfaceVolume
      -   Raster and TIN/Terrain


 •   TIN/Terrain specific
      -   Polygon Volume
      -   Surface Difference
      -   Extrude Between
Volume Below Plane
Volume Below Plane
Demo
Enhancements in ArcGIS 10.0

 •   More tools operate directly on terrain datasets
 •   Line of Sight with Buildings
 •   Import TINs from LandXML (CAD)
 •   Skyline

 •   Analysis with 3D vector features:
      -   See 3D Analyst: Feature and Volumetric Analysis
          Tech workshop (Wed 3:15 Room 1 A/B)
            Questions?



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posted:9/24/2012
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