Topographic Lidar Survey of the Alabama, Mississippi, and Southeast Louisiana Barrier Islands, from September 5 to October 11, 2012 -- Bare Earth Digital Elevation Models

The USGS conducted ground surveys in a small area on Chandeleur Island on September 6, 2012, one on bare earth and another in mixed bare earth and vegetated areas. The USGS calculated a vertical root mean square error (RMSEz) of 0.072 m and an offset of 0.007 m using interpolated 2-m by 2-m resolution grid surfaces made from lidar bare-earth data and combined USGS ground surveys. The contractor was required to achieve a fundamental vertical accuracy (FVA) of 24.5 centimeters (cm), 95 percent (12.5 cm RMSEz); a consolidated vertical accuracy (CVA) of 36.3 cm, 95th percentile; and a target value for supplemental vertical accuracies (SVA) of 36.3 cm, 95th percentile. Aero-Metric's vertical accuracy assessment was as follows: The FVA of the LAS Swath Data achieved 5.0 cm at a 95 percent confidence level with an RMSE of 2.5 cm utilizing (2280) ground survey check points provided by the USGS. The SVA results in an area of open terrain achieved 4.8 cm at the 95th percentile where (2280) ground survey check points provided by the USGS were evaluated. The SVA results in an area of vegetation achieved 10.7 cm at the 95th percentile where (2421) ground survey check points provided by the USGS were evaluated. The CVA results for all land cover classes, ground and vegetation combined, achieved 7.3 cm at the 95th percentile where (4700) checkpoints were evaluated. The USGS also conducted a terrestrial lidar survey on Dauphin Island, Louisiana, on September 3, 2012. The USGS calculated an RMSEz of 0.32 m and an offset of 0.27 m using interpolated 2-m by 2-m resolution grid surfaces from the airborne lidar bare-earth data and the terrestrial lidar survey.