Working with Breaklines in LP360

Data Modeling - Why is it important?

When collecting data, we “sample” the real world. However, there is spacing between sample points. To visualize the point cloud as a surface, we need to “fill in” the space between the points.

A breakline is a vector-based feature (a point, polyline or polygon) added to a 3D model to improve the representation of the real world. 

If you are interested in a more in-depth look at breaklines, please review our 5 part series:

• Breaklines in LP360 - Part 1
• Breaklines in LP360 - Part 2
• Breaklines in LP360 - Part 3
• Breaklines in LP360 - Part 4
• Breaklines in LP360 - Part 5

Examples of Breakline Usage in Data Modeling

• Edge definition such as “edge of pavement” for roads, building footprints, edge of streams
• Shorelines of water flat bodies
• Talweg (also thalweg, the channel center) definition for streams
• Edge of bank of a flowing river or stream (a “double line drain”)
• Zero slope centerline of roads (the crown)
• Edges of highwalls in mining
• Stockpile base definition (the stockpile “toe”)
• Ground survey points in areas where the sampling system (for example, photogrammetric modeling) did not penetrate through vegetation to the ground

Preparing features for breakline enforcement

In LP360, a conflation task defines how elevations are populated onto the geometry for vector data such as stream centerlines, ponds, lakes, or buildings. When creating a new breakline feature layer, a conflation methods needs to be use to get the correct elevation values.

Conflation Methods:

• Summarize Z
  • Most common Z values: Constant Z and Surface Z
• Drape
  • Pure Drape
  • Create Vertex every X Map Units
  • Get Z for existing vertices
• Downstream Constraint
  • Used to ensure stream/river/drain breaklines flow in a downstream direction
• Retaining Wall
  • Assigns elevation values to the top and bottom of wall lines

General Breakline Enforcement Workflow

1. Import LAS using Add Files

2. Create or Import your Breakline Feature Layer

   • If you're importing your breakline feature, right-click the imported feature in the Map View > Apply Auto-Z (Surface) or Apply Constant
   • If you're creating a new feature layer, use Create Feature Layer  on the Feature Edit Tab of the ribbon.
     
     • Polylines are used for hard surface breaks (example: curbs)
       • Use the Drape Conflation Method
     • Polygons are used for soft surface breaks (example: waterbody)
       • Use the Summarize Z Conflation Method

3. How to Conflate

   • Open the Feature Edit Options dialog found on the Feature Edit tab, then navigate to the Auto Z tab.
     • Click the ellipse (...) button next to Conflation Task to open the PCT to select your method type.
       • For Polylines (hard surface breaks)
         • Use the Drape Conflation Method
       • For Polygons (soft surface breaks)
         • Use the Summarize Z Conflation Method
   • Use the Create Feature tool on the Feature Edit Tab of the ribbon to digitize a feature of interest. Be sure to enable the Auto-Z function. 
   • Begin digitizing the desired feature

4. Perform Buffer Classification

   • Buffer Classification allows the algorithm to use your feature to draw the surface. If no buffer class is applied, there may be conflict between the points and the feature.
   • Use Classify by Feature PCT to classify points surrounding the feature. For preset PCTs, review the Download Data section of the Exporting to CAD page.
     • For Hard Breakline Features, one PCT classification is needed.
       • Input Points Filter set to only Ground (Class 2) 
       • Use the following Spatial Relationship:
         • Within a Distance of Feature (buffer)
           • Destination Class: Ignored Ground
     • For Soft Breakline Features, two PCT classifications are needed Note: creating a Macro PCT that contains two Classify by Feature PCTs is helpful).
       • Input Points Filter set to Ground (Class 2) and Water (Class 9 - if applicable)
       • Use the following Spatial Relationships: 
         • First PCT: Within a Distance of Feature (buffer)
           • Destination Class: Ignored Ground
         • Second PCT: Completely within (classify interior)
           • Destination Class: Water
     • Apply all changes to your PCT(s).
     • Execute By Feature Layer on the Point Tasks tab of the ribbon.

5. Enforce Your Breaklines

   • Hold down the Ctrl Key and click the Breakline Enforcement  tool on the Map Toolbar to open the settings.
   • Check the box next to Use Breakline Enforcement
     • Select your feature layer
   • Check the box next to Perform On_The_Fly Topology Corrections
     • Press Modify Classes
       • Select the Buffer class used
       • Press OK
     • Press Apply and close the dialog