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Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
Ilmf2010 breaklines
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Ilmf2010 breaklines

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Transcript

  • 1. Breaklines: What Are They and How Are They Used March 4, 2010
  • 2. Presentation Overview  Breaklines – What Are They  Breakline Issues  Breaklines for Digital Terrain Model Development  Breaklines for Contour Development  Example Project Breakline Specifications  Water Resources Applications – ESRI Arc Hydro Extension  Results without Breaklines  Results with Breaklines
  • 3. Breaklines What Are Breaklines and Why Are They Needed?
  • 4. Breakline Definition  Reflect abrupt changes in the terrain and control surface behavior by acting as a barrier to the interpolation of a TIN model  Breaklines enhance the accuracy of the surface model in areas where LiDAR points are not adequate to accurately depict the surface.  One driver of contour aesthetic properties  Generally two types of breaklines  Traditional breakline features to meet accuracy specification  Cliffs, ridgelines, hydro features, road edges, levees and retaining walls – not used as much as in the past  Hydro-enforced breaklines to define the hydrology,  Streams, ponds, lakes, ditches – becoming more common  Some overlap between the two types
  • 5. Breakline Collection Approaches Photogrammetric  Traditional approach  Utilizes stereo models (3D)  Aerial imagery  Date doesn’t match LiDAR  Requires two lines of sight  LiDARgrammetry - LiDAR intensity images  Can be expensive
  • 6. Breakline Collection Approaches (cont.) Heads-up (2D)  Horizontal placement based on LiDAR  Bare-earth LIDAR for vertical (Z)  Very effective terrain modeling in vegetated areas  Requires only one line of sight  Less costly in development vs. traditional methods  Faster than traditional methods  Meets FEMA surface accuracy requirements
  • 7. Hydro Breaklines  Hydro breaklines allow for DTM development that provides accurate terrain for watershed modeling, hydraulic & hydrologic modeling, stormwater and drainage area delineation, and stream channel geomorphology studies  Enforce stream channels and ditches into DTM  Breaklines go around islands in rivers, lakes, etc.  Waterbodies are flattened
  • 8. Dual vs. Single Breaklines
  • 9. Dual Line Breaklines  Upper part of the channel has no breaklines  Lower part of the channel has dual breaklines  River channel flatten with breaklines on each side of the channel at waters edge
  • 10. Hydro Breaklines - Waterbodies  Waterbodies usually have a breakline compiled around the water’s edge  LiDAR points inside breakline are reclassified and waterbody is flattened – same elevation  Thisis done for TIN creation, DTM generation, contour development, and aesthetic
  • 11. Breakline Issues
  • 12. Hydro Connectors  Culverts and Dam Outlets – Special Considerations Hydro connectors shown as yellow lines
  • 13. Breaklines for Braided Rivers  Braided rivers create special problems, specifications need to be defined  Treatas multiple dual breaklines Platte River in Nebraska
  • 14. Breaklines for Braided Rivers (cont.) Platte River in Nebraska
  • 15. Breaklines and Wetlands DEM DTM  How should wetlands be handled?  Breakline only around water, don’t include vegetation?
  • 16. Buffer Around Breaklines  Use a buffer to remove bare-earth points around breaklines, otherwise artificial dams are created  Recommend 5-ft outside buffer (based on our experience)
  • 17. Breaklines and Digital Terrain Model Development
  • 18. DTM Results No breaklines Breakline enforced
  • 19. DTM Quality (cont.) With LiDAR data, if breaklines are not specified, hydro features will not be as well defined, can cause modeling errors With Breaklines Without Breaklines
  • 20. Breaklines and Contour Development
  • 21. Contour Results – DEM vs DTM Contours without breaklines Contours with breaklines
  • 22. Contour Results – 1-ft Interval Contours without breaklines Contours with breaklines
  • 23. Breakline Project Samples
  • 24. Example Project – Wichita/Sedgwick County, KS Breaklines Specifications Linear Features – rivers, streams, ditches  Minimum length = 200 ft  Double line breakline – channels over 4 ft wide at base  Breaklines around islands  Single line stream breaklines under 4 ft wide at base  Stream channel breaklines only at water/land interface  Culverts & dam outlets – hydro connectors – separate feature class
  • 25. Wichita Example Breaklines for Waterbodies Waterbodies: Lakes, Ponds (¼ acre or larger)
  • 26. Wichita Example – Other Breaklines Traditional Breaklines  Edge of pavement breaklines along major roads  Breaklines along top of dams, levees, dikes
  • 27. Wichita Example – Breakline Density
  • 28. Wichita Example – Breakline Deliverables  ESRI Geodatabase  Dataset  Feature Classes
  • 29. Missouri Example – LiDAR for Flood Mapping Hydro-Enforced Breaklines Only  Minimum length of 300- ft  Breaklines z-values from bare-earth LiDAR  Dual breaklines for streams/ditches > 2- meters  Single breaklines for streams/ditches < 2- meters  Stream/ditch breaklines cut through culverts and dam outlets
  • 30. Missouri Example – LiDAR for Flood Mapping (cont.)  Waterbody breaklines for ½ acre or greater
  • 31. Missouri Example - Breakline Density
  • 32. Missouri Example – Breakline Deliverables  Shapefiles  Linear features – includes streams, rivers, ditches  Polygons - waterbodies
  • 33. Water Resources Applications: ESRI Arc Hydro Drainage Line Comparison
  • 34. DEM vs Hydro DTM DEM Hydro DTM
  • 35. Fill Grid Using DEM & Arc Hydro Drainage Lines
  • 36. Hydro Breaklines and Hydro Connectors
  • 37. Hydro Fill Grid and Arc Hydro Drainage Lines  Dark blue lines – Arc Hydro Drainage Lines  YellowLines – Hydro Connectors
  • 38. Arc Hydro Drainage Line Comparison  Dark blue lines – with breaklines  Cyan lines – without breaklines  Yellowlines – Hydro Connectors
  • 39. Arc Hydro Catchment Comparison  Redlines – catchments from DEM  Yellow lines – catchments from DTM  DTM is background
  • 40. Arc Hydro Comparison Results #2  Dark blue lines – with breaklines  Cyan lines – without breaklines  Yellow Lines - Hydro Connectors  Results show flow in different directions
  • 41. Final Thoughts When do you need breaklines? Types of breaklines?
  • 42. Questions Kenny Legleiter Senior Government Account Manager 303-353-3837 Kenny.legleiter@merrick.com

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