Lab 6

Introduction

The purpose of this lab is to perform a QA/QC of a topobathy lidar point cloud, create and generate a conflate a breakline for a shoreline as well as configuring the enforcement of that breakline for topo-bathy deliverables.

Methods

The first process in this lab was to correct a topobathy lidar point cloud dataset in Delta County, Michigan. This dataset had many classification errors due to both commission and omission errors. These areas where highlighted in LP360 by digitizing areas around dataset errors and labeling these areas either as omission or commision using the create feature class tool. For example, there were many areas in the Lake Michigan that had been wrongly classified as ground points due to the reflection of LiDAR pulses suspended sediments. There were also many inland water bodies that had been classified as ground points. Omission errors included large areas along the coast line that been left unclassified.

Once these areas were identified the errors on the coastline were corrected using manual classification. This was done to ensure that the breaklines would have enough ground points to conflate the polyline feature accurately.  After this process was completed, a polyline feature was created for shoreline. Then a filter for the was applied to data displaying only ground and 31 reserved points and the LAS dataset was displayed via a TIN. Using the conflate manager a new task was created using the drape method for the breaklines with vertices being created every 5 map units. The polyline was drawn tracing the shoreline using the ground points. Following the creation of the polyline, a polygon feature class was created using the same parameters and instead of tracing the shoreline, the polygon feature traced the rest of the dataset along with the shoreline.

Once the polyline and polygon were created, they were then brought into LP360 where they were conflated over LAS tiles (figure 1).

Figure 1. Breaklines created in ArcMap used to create DTM in LP360

Once the LAS files and newly created breaklines were brought into LP360 the surface was then exported as DTM. The source points for the DTM were ground points, roads, and 31 reserved. The surface method was a TIN and breaklines enforced using the newly created polyline and polygon. Using these parameters a new DTM was created for Delta County dataset.

Results

DTM created in LP360 from the breaklines created in ArcMap 

Sources
The materials for this lab were provided by Dr. Cyril Wilson of the University of Wisconsin-Eau Claire