Project Description

Lake Purdy is a 990 acre reservoir on the southeastern side of Birmingham, AL and is owned by the Birmingham Water Works Board (BWWB). Wiser was engaged to provide a detailed and highly accurate topographic survey covering the lakeshore and surrounding 12,000 acres in order to study the impact of a change in the pool elevation for additional storage.

Due to the size of the area, accuracy requirements and heavy tree cover, helicopter mounted aerial LiDAR was utilized for data acquisition. Wiser post-processed and classified the resulting data including bare earth ground distinction. The point cloud was then QC analyzed versus field collected RTK GPS points around the entire perimeter of the project. The analysis showed an average error of 0.13’ which was well within the 0.5’ accuracy requirement for the project. The point cloud was then classified for model key points to produce a data set with the proper balance of accuracy to data density.

One foot interval contours and digital elevation and terrain models were developed from the point cloud data. The deliverables included several formats of this data including ESRI ArcGIS DEM and Shapefiles, MicroStation Geopak TIN and Autodesk Civil 3D TIN.