Breaklines: What Are They
 and How Are They Used




                        March 4, 2010
Presentation Overview

 Breaklines   – What Are They
 Breakline   Issues
 Breaklines   for Digital Terrain Model Develo...
Breaklines




What Are Breaklines and
Why Are They Needed?
Breakline Definition
 Reflect abrupt changes in the terrain and
  control surface behavior by acting as a
  barrier to th...
Breakline Collection Approaches
    Photogrammetric
   Traditional approach
   Utilizes stereo models
    (3D)
        ...
Breakline Collection Approaches (cont.)
Heads-up (2D)
   Horizontal placement based
    on LiDAR

   Bare-earth LIDAR fo...
Hydro Breaklines


   Hydro breaklines allow for DTM
    development that provides
    accurate terrain for watershed
   ...
Dual vs. Single Breaklines
Dual Line Breaklines


   Upper part of the
    channel has no
    breaklines
   Lower part of the
    channel has dual
...
Hydro Breaklines - Waterbodies

 Waterbodies usually
 have a breakline
 compiled around the
 water’s edge
 LiDAR  points...
Breakline Issues
Hydro Connectors

 Culverts
         and Dam Outlets – Special
 Considerations




 Hydro connectors shown as yellow lines
Breaklines for Braided Rivers

 Braided rivers
 create special
 problems,
 specifications
 need to be
 defined
 Treatas ...
Breaklines for Braided Rivers (cont.)




 Platte River in Nebraska
Breaklines and Wetlands
DEM               DTM

                             How    should
                               ...
Buffer Around Breaklines
   Use a buffer to remove bare-earth
    points around breaklines,
    otherwise artificial dams...
Breaklines and Digital
Terrain Model Development
DTM Results




       No breaklines




Breakline enforced
DTM Quality (cont.)

With LiDAR data, if breaklines
are not specified, hydro features
will not be as well defined, can
cau...
Breaklines and
Contour Development
Contour Results – DEM vs DTM

Contours without breaklines   Contours with breaklines
Contour Results – 1-ft Interval

                           Contours without
                            breaklines




Co...
Breakline Project
    Samples
Example Project – Wichita/Sedgwick County, KS
           Breaklines Specifications
Linear Features – rivers,
 streams, di...
Wichita Example Breaklines for Waterbodies

   Waterbodies: Lakes, Ponds (¼ acre or larger)
Wichita Example – Other Breaklines

Traditional Breaklines
 Edge of pavement
 breaklines along
 major roads
 Breaklines
...
Wichita Example – Breakline Density
Wichita Example – Breakline Deliverables

 ESRI     Geodatabase
    Dataset
        Feature Classes
Missouri Example – LiDAR for Flood
                       Mapping
Hydro-Enforced
 Breaklines Only
   Minimum length of 30...
Missouri Example – LiDAR for Flood
               Mapping (cont.)
   Waterbody breaklines for ½ acre or greater
Missouri Example - Breakline Density
Missouri Example – Breakline Deliverables


 Shapefiles

    Linear features – includes streams, rivers, ditches
    Po...
Water Resources Applications:
ESRI Arc Hydro Drainage Line Comparison
DEM vs Hydro DTM




DEM




                         Hydro DTM
Fill Grid Using DEM & Arc Hydro Drainage
                  Lines
Hydro Breaklines and Hydro Connectors
Hydro Fill Grid and Arc Hydro Drainage
                          Lines

 Dark blue
 lines – Arc
 Hydro
 Drainage
 Lines
...
Arc Hydro Drainage Line Comparison

 Dark blue
 lines – with
 breaklines
 Cyan lines –
 without
 breaklines
 Yellowline...
Arc Hydro Catchment Comparison


 Redlines –
 catchments
 from DEM
 Yellow
       lines –
 catchments
 from DTM
 DTM is...
Arc Hydro Comparison Results #2
 Dark blue
 lines – with
 breaklines
 Cyan lines
 – without
 breaklines
 Yellow
 Lines ...
Final Thoughts




When do you need breaklines?
   Types of breaklines?
Questions



          Kenny Legleiter
Senior Government Account Manager
           303-353-3837
   Kenny.legleiter@merric...
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Ilmf2010 breaklines

  1. 1. Breaklines: What Are They and How Are They Used March 4, 2010
  2. 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. 3. Breaklines What Are Breaklines and Why Are They Needed?
  4. 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. 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. 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. 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. 8. Dual vs. Single Breaklines
  9. 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. 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. 11. Breakline Issues
  12. 12. Hydro Connectors  Culverts and Dam Outlets – Special Considerations Hydro connectors shown as yellow lines
  13. 13. Breaklines for Braided Rivers  Braided rivers create special problems, specifications need to be defined  Treatas multiple dual breaklines Platte River in Nebraska
  14. 14. Breaklines for Braided Rivers (cont.) Platte River in Nebraska
  15. 15. Breaklines and Wetlands DEM DTM  How should wetlands be handled?  Breakline only around water, don’t include vegetation?
  16. 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. 17. Breaklines and Digital Terrain Model Development
  18. 18. DTM Results No breaklines Breakline enforced
  19. 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. 20. Breaklines and Contour Development
  21. 21. Contour Results – DEM vs DTM Contours without breaklines Contours with breaklines
  22. 22. Contour Results – 1-ft Interval Contours without breaklines Contours with breaklines
  23. 23. Breakline Project Samples
  24. 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. 25. Wichita Example Breaklines for Waterbodies Waterbodies: Lakes, Ponds (¼ acre or larger)
  26. 26. Wichita Example – Other Breaklines Traditional Breaklines  Edge of pavement breaklines along major roads  Breaklines along top of dams, levees, dikes
  27. 27. Wichita Example – Breakline Density
  28. 28. Wichita Example – Breakline Deliverables  ESRI Geodatabase  Dataset  Feature Classes
  29. 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. 30. Missouri Example – LiDAR for Flood Mapping (cont.)  Waterbody breaklines for ½ acre or greater
  31. 31. Missouri Example - Breakline Density
  32. 32. Missouri Example – Breakline Deliverables  Shapefiles  Linear features – includes streams, rivers, ditches  Polygons - waterbodies
  33. 33. Water Resources Applications: ESRI Arc Hydro Drainage Line Comparison
  34. 34. DEM vs Hydro DTM DEM Hydro DTM
  35. 35. Fill Grid Using DEM & Arc Hydro Drainage Lines
  36. 36. Hydro Breaklines and Hydro Connectors
  37. 37. Hydro Fill Grid and Arc Hydro Drainage Lines  Dark blue lines – Arc Hydro Drainage Lines  YellowLines – Hydro Connectors
  38. 38. Arc Hydro Drainage Line Comparison  Dark blue lines – with breaklines  Cyan lines – without breaklines  Yellowlines – Hydro Connectors
  39. 39. Arc Hydro Catchment Comparison  Redlines – catchments from DEM  Yellow lines – catchments from DTM  DTM is background
  40. 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. 41. Final Thoughts When do you need breaklines? Types of breaklines?
  42. 42. Questions Kenny Legleiter Senior Government Account Manager 303-353-3837 Kenny.legleiter@merrick.com

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