ArcView 3D Analyst

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ArcView 3-D Analyst
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Triangulated Irregular Network (TIN)
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A Mesh of Triangles
Triangle is the only polygon that is always
planar in 3-D
Lines
Surfaces
Points
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Tin Triangles in 3-D
(x3, y3, z3)
(x1, y1, z1)
(x2, y2, z2)
z
y
Projection in (x,y) plane
x
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Delauney Triangulation
Maximize the minimum interior angle of
triangles No point lies within the circumcircle
of a triangle
Yes
No
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Circumcircle of Triangle

• Draw the perpendicular bisectors of each edge of
  the triangle
• Circumcircle is centered on their intersection
  point
• Radial lines from center have equal length

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Inputs for Creating a TIN

• Hard breaklines define locations of abrupt
  surface change (e.g. streams, ridges, road kerbs,
  building footprints, dams)
• Soft breaklines are used to ensure that known z
  values along a linear feature are maintained in
  the tin.

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TIN for Waller Creek
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TIN with Surface Features
Classroom
UT Football Stadium
Waller Creek
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A Portion of the TIN
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Input Data for this Portion
Mass Points
Soft Breaklines
Hard Breaklines
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TIN Vertices and Triangles
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TIN Surface Model
Waller Creek
Street and Bridge
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3-D Scene
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3-D Scene with Buildings
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Watershed Modeling With TINs
Slides from Dr James Nelson Brigham Young
University Sponsored by National Highway
Institute US Department of Transportation
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Work Flow
Tin-based Watershed Delineation
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Flow On a Triangle
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Flow On a TIN
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Defining Basins
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Computing Basin Data

• Area
• Slope
• Flow Distances
• Slopes
• Aspect
• Stream Lengths
• Slopes
• Others

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Modifying Basins
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Ten Steps Using TINs

• 1. Background Elevation
• 2. Smooth Elevations
• 3. Conceptual Model
• 4. Redistribute Vertices
• 5. Create TIN
• 6. Edit TIN
• 7. Add Interior Outlets
• 8. Define Basins
• 9. Refine TIN
• 10. Compute Basin Data

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1 Background Elevation

• TINs
• Digitized
• XYZ Data
• DEMs

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2 Smooth Elevations

• TINs or DEMs

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3 Conceptual Model
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4 Redistribute Vertices

• From Coarse to Fine

• From Fine to Coarse

• Unequal Distribution

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5 Create TIN
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6 Edit TIN

• Flat Triangles
• Pits

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7 Add Sub-basin Outlets
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8 Define Basins
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9 Refine TIN
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10 Compute Basin Data

• Basins
• Area
• Slope
• Avg. Elevation
• Length
• Streams
• Length
• Slope

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Ten Steps Using TINs

• 1. Background Elevation
• 2. Smooth Elevations
• 3. Conceptual Model
• 4. Redistribute Vertices
• 5. Create TIN
• 6. Edit TIN
• 7. Add Interior Outlets
• 8. Define Basins
• 9. Refine TIN
• 10. Compute Basin Data

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TIN Strengths

• Automated Basin Delineation with Parameter
  Calculations
• Adaptive Resolution
• you can use most any elevation data source
• Urban Areas
• where small variations in flow can be significant
• It Was in WMS First
• reservoir definition, storage capacity curves,
  time area curves, flood-plain delineation

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TIN Weaknesses

• Lack of Available Data
• With conceptual model approach this is not such a
  big factor anymore
• Extra Steps
• Local editing