High Resolution LiDAR Data for the Lake Tahoe Watershed

Tahoe Regional Planning Agency

The Tahoe Regional Planning Agency (TRPA) with the assistance of the U.S. Geological Survey (USGS) put out an RFP to establish highly accurate base mapping of the entire Lake Tahoe Watershed using Light Detection and Ranging (LiDAR) methods and technology. The RFP included very specific and rigorous specifications to obtain the massive amount of data required for the mapping effort. This base mapping effort with USGS’ support is to provide a highly accurate baseline map of the entire Tahoe Watershed using very dense, high resolution, airborne LiDAR scanning of the terrain. The effort will be repeated periodically to detect and measure changes and other influences affecting the very sensitive Lake Tahoe Watershed. ANDREGG was approached by several LiDAR mapping firms to provide the highly accurate surveying services required of the project.

Because of the firm’s proximity to the region, with an office in Truckee, along with extensive experience in providing highly accurate LiDAR control and QA/QC, ANDREGG was selected to provide all required surveying for the selected LiDAR mapping team. Using both 1 person and 2 person crews, and judicious planning and coordination ANDREGG established and surveyed nine primary base stations for the LiDAR airborne GPS base mapping control surrounding the entire Lake Tahoe Basin, and over 50 Ground Control Points. The Ground Control Points (GCP) were established within the mapping region to both calibrate and provide blind QA/QC points to ensure the accuracy of the LiDAR bare earth digital terrain model. The blind QA/QC ground control points were compared with the LiDAR returns for the area and residuals were computed for each to determine compliance with the very rigid requirements and specifications of the project. The project data had to be obtained during a period of minimal snow cover. The project was challenging due to several factors including the highly variable elevation and altitude of the region, the narrow window of opportunity to fly, limited roadway access around the region, tourist traffic, large tree obstructions, and the very rigorous project specifications. ANDREGG completed and performed all required surveying and data processing and checks within the limited time frame and within budget.