Introduction
In many cases there are not many LIDAR returns from the surface of waterbodies, and sometimes none at all. In some situations, it is useful to have points that can represent the surface of these waterbodies. LP360 can be used to generate points for these areas and mark them as synthetic points.
Methodology
- Generate breaklines around waterbodies using the, the Feature Edit Toolbar, LP360 Sketch Tool or by conflating existing line work.
- Export surface points using Export Wizard
Export Surface Points
- Setting Source Points to all classes unselected will cause the surface of the waterbodies to be generated from the polygons alone, without influence of any misclassified points.
- Under Breakline Enforcement, be sure to enable enforcement to use the features in the shapefile with the elevation attribute as applicable for the generation process followed when creating the breaklines.
Breakline Enforcement for Surface Export
- In step two of the wizard, use the Cookie Cut by Polygon option and provide your waterbodies shapefile in order to generate one ASCII text file per waterbody. Using the ID field will ensure each gets assigned a unique name.
Export Surface Points – Step 2
- In step three, provide the folder to create these exported files.
- Convert surface points to LAS format using the Import from ASCII tool and use the Force all points within all files to classification “9-Water”.
- Add the surface points LAS files to a new LAS_Layer in LP360.
- Flag the surface points as “Synthetic” using a Basic Filter Point Cloud Task.
Mark As Synthetic
- Export the points again from LP360 using the Export Wizard to the same LAS Format and PDRF as your existing data. If not in LAS v1.4 PDRF 6 or higher you will need to also convert your dataset to that in order to be able to do the next step. See Putting LIDAR Data on a Single Layer for more information.
- Add the exported surface points to the existing LAS_Layer containing the rest of your dataset.
