Info

Traditional Photogrammetry & Lidar Can Work Together

Western Air Maps combined traditional photogrammetry and LIDAR technology as a solution to challenging target terrain during their first LIDAR project. Under contract with the US Army Corps of Engineers-Kansas City District (KCD), WAM used LIDAR scanning and conventional aerial photogrammetry to develop an accurate topographic and planimetric picture of a 4,600 acre training facility at the Fort Riley Army Base in Kansas. It was the first LIDAR project for KCD as well, and required aerial acquisition during July, with full leaf-on vegetation, to meet the planning and design schedule With a planned expansion of Fort Riley’s Digital Multi-Purpose Training Range (DMPTR) and Multi-Purpose Range Complex (MPRC), KCD required new topographic and planimetric data meeting the design accuracy requirement of 1’ contours and line-of-sight visualization for range targeting systems. The facilities train Fort Riley’s 24th Infantry Division (Mechanized) as well as Army and National Guard Units. The DMPTR and MPRC offer units uninterrupted weeks during the year to train. Dense July foliage could not be removed via a controlled burn because of the facility’s constant training schedule. Photo acquisition had to be planned so it would not interrupt the training schedule. Team members had to stay within marked safety zones while conducting set-up survey ground work, as the site contained unexploded ordinance. The range also contained a natural feature unique to the area; some of the last tallgrass prairie in the country. According to researchers at Kansas State University, the tallgrass canopy reaches over 2.5 meters in height. It is very dense, and team members expressed concern that it would produce false ground data. To compensate for the prairie, WAM designed a QA/QC program with 188 surveyed ground check points. WAM subcontracted with LandAir Mapping, Inc. to complete LIDAR data acquisition. LIDAR systems can scan through dense foliage for terrain elevation, and can be used any time of day. Little activity occurred on the training range during the night, so LIDAR data acquisition was conducted then. WAM performed a 100% QC verification internally using TerraScan software for the “bald earth” surface model LandAir produced. Statistically 90% of elevation differences between LIDAR shots and ground control points were less than 6”, a RMSE of 0.238’ for the entire dataset, complying iwht the VMAS standard for 1’ contour mapping. By isolating the 10% outliers, the RMSE drops to 0.228 feet; meeting NSSDA standards, which indicates a very good overall topographic accuracy of the dataset. Fort Riley served as a training ground for WAM’s second LIDAR project; mapping 640,000 acres in Michigan for the USACE-Detroit District. The Fort Riley project proved that traditional photogrammetry can work effectively with LIDAR data to produce solutions in dense, diverse environments.