Drape Polygon (DraPol)
Type: Interactive/Batch Application
Creates a Digital Terrain Model (DTM surface) based on a user identified or user digitized polygon and optional three-dimensional symbols. VrPoints (LiDAR) or Symbols may be draped to this surface, or the surface, along with an elevation tolerance, may be used to re-classify VrPoints above or below the surface. An additional option includes the deletion of VrPoints or Symbols that fall within the polygon and are above or below the user defined tolerance. The polygon is referred to as the boundary polygon.
The use of Drape Polygon for re-classification of VrPoints should be considered an editing or refinement tool to fix classification errors from previous batch applications. It should not be considered a primary tool for the initial classification of VrPoints (LiDAR). Drape Polygon considers VrPoints (LiDAR) and Symbols only.
NOTE: Drape Polygon considers the Vr Point Display (PoiDis) parameters when processing VrPoints. If a VrPoint is not displayed, it will not be considered, even if it is specified.
Original VrPoint (LiDAR) point data before re-classification
VrPoint (LiDAR) point data after re-classification
The examples above show VrPoint (LiDAR) point data with classifications on a building that are incorrect. The next example shows the result of Drape Polygon using the Drape Action of Classify to re-classify VrPoints that are over a user defined elevation tolerance above or below the DTM surface.
The Drape Polygon Menu Keys
Drape Polygon – Main
The Drape Polygon parameter dialog
Workspaces to consider - Defines the workspaces to consider when identifying points for change. This may be set to "Current only", or "All Open".
Drape action - Three options are available when considering VrPoints against the DTM surface created by the polygon and optional symbols:
Classifications to search (NumLine) - Defines the classifications to search for when processing VrPoints. Normally points that are displayed are considered but using this parameter allows all points to be displayed while only the classifications defined will be considered for modification. Leaving the field blank will indicate that all VrPoints that are displayed will be considered. A Number Line may be used to define this parameter.
Use symbols when creating the DTM surface? - When active, symbols that are in the "Layers containing symbols" and are within the boundary polygon will be used along with the points on the polygon to define the DTM surface.
Layers containing symbols to use for DTM surface (NumLine) - If the "Use symbols when creating DTM surface" is set to Yes then this parameter will be used to define the layers containing symbols to be used to supplement the DTM surface. A Number Line may be used to define more than one layer.
New classification - If the "Drape action" is set to "Classify VrPoints" then the VrPoints that meet the search criteria are changed to the Classification number defined by this parameter.
Z tolerance - If the "Drape action" is set to "Classify VrPoints" or "Delete VrPoints" or "Delete Symbols" then this parameter defines the minimum vertical distance above or below the DTM surface that VrPoints or symbols must be to be considered for re-classification or deletion.
Change data above or below DTM surface - If the "Drape action" is set to "Classify VrPoints" or "Delete VrPoints" or "Delete Symbols" then this parameter defines the side of the DTM surface to modify data. Options are Above or Below.
Layers containing symbols to drape or delete - If the "Drape actions" is set to "Drape Symbols" or "Delete Symbols", this parameter is used to define the layers containing symbols that are draped or deleted if they fall within the boundary. A Number Line may be used to define more than one layer.
Minimum elevation - Defines the minimum elevation for VrPoints or Symbols to be considered.
Maximum elevation - Defines the maximum elevation for VrPoints or Symbols to be considered.