Lab 5

The purpose of this lab is to create, identify and fix topological errors in breaklines, conflate breaklines, inspect breaklines elevation data, configuration of surface features based upon breaklines. 

Methods

The first section of the lab, I was given a shapefile that had outlined all the water bodies in the the study area. From this shapefile topological errors were found and corrected in ArcMap. This was done to ensure that there would not be errors in breakline enforcement between the breaklines and the LAS point cloud. If there were areas where there were topological errors it lead to undesirable results when hydro-flattening the water bodies in the study area.

Once the topology of the lines was corrected, the breaklines could then be conflated. To begin, the LAS file was displayed in a TIN surface. Then a new conflation point cloud task was created using the topologically corrected shapefile from the first section of the lab. The ground and water points were set as the source points for the conflation. The conflation method used was ponds and lakes was Summarize Z. This was used to ensure that the Z values for the conflated breakline would create a homogeneous elevation so that the water bodies could be hydro-flattened. For Islands and rivers the Drape conflation method was used. Then the conflation task was run. Once the breaklines had been conflated, the newly conflated brealines were brought into ArcMap where a new z elevation field was created and the z value geometry was calculated, giving the elevation values for the breaklines. Then the breaklines where used using Breakline Enforcement to hydro-flatten the water bodies. Once this was done smooth contours where generated for the image at an interval of 5 map units. This was done to ensure that the hydro-flatten water bodies were in fact flat and did not have elevation errors. Then a digital terrian model of the LAS tiles was generated using the classified ground points.

Once this was completed, we were given a LAS dataset for the city of Eau Claire. This LAS dataset was imported into ArcMap where we then created a new polygon and polyline feature that were used to create conflated breaklines for the Chippewa River. In each of these features, fields were created for the water type, min Z, mean Z, and maximum Z values. Once the features were created, they were then digitized over a TIN surface created from the LAS file. The polygon outlined the river and the polyline was digitized down the center of the river. The polyline was digitized down the center of the river so that a downstream constraint could be calculated for the river. Once the breaklines were created the River-Flattening  tool was to hydro-flatten the Chippewa River.