Tesla, Inc., through its Solar City subsidiary, contracted McKim & Creed to create a rooftop survey of three sites in San Antonio, Texas for a new solar installation. In order to plan the installation, it was important to know the location and shape of all features on the roofs, including the height of each object. This enabled the client to determine if the roof objects would obstruct the view of each panel. Many of these items were as small as outlet boxes, which required a high-fidelity approach.
McKim & Creed determined the best approach would be to utilize our post-processed kinematic (PPK) Loki UAS system to collect ultra-high resolution imagery to perform stereo compilation. This is a method of looking at an image pair to derive 3D vector information. McKim & Creed flew the three rooftop locations at a ground sampling distance (GSD) of half a centimeter. This imagery, along with the survey grade GPS from the PPK system, was used in conjunction with ground verification shots to create an aerotriangulation solution. Compilers then extracted the 3D vector work for the entire roof sites and were able to easily discern small objects such as outlet boxes on the roof. CAD drawings were created for each roof survey utilizing this method. The results were verified by comparison to traditional survey shots at an accuracy of less than 1/10th of a foot.
Using UAS improved job safety by minimizing time any personnel needed to be on the rooftops. As an added benefit, a high-resolution ortho photograph was produced of the sites, which further aided in the design planning.