Two data sets of a made-up crime scene were acquired with quadcopters from Aeryon Labs (225 images) and Draganfly (212 images). The ground sampling distance was less than 1 cm in order not to miss any details. The full flight took less than thirty minutes including the pre-flight preparation. Eight yellow evidence markers were placed around the collision scene, indicating the location where all evidence was found.
See the densified 3D point cloud on Pointscene.com platform embedded below:
View HD version on Pointscene.com Google Chrome, Mozilla Firefox and Safari browsers supported)
In order to improve the global accuracy of the final results, several points were measured with kinetic GPS and total station. These points were picked from corners of the vehicles, the feature objects, and the evidence markers. They were imported into the software and used either as ground control points, manual tie points or check points. In addition, a terrestrial laser scanner was set up in several locations to scan over the entire scene to be used for quality assessment of the UAV results.
Pix4Dmapper’s total processing time was approximately 2 hours on a laptop with a core i7 and 8GB RAM. A densified point cloud, digital surface model (DSM) and orthomosaic were generated.
The reconstructed results either exactly match or are within one centimeter accuracy when compared with traditional methods. Detailed comparisons of results can be found in the White Paper (http://pix4d.com/wp-content/uploads/2013/04/Pix4D-White-Paper_UAV-based-CSI.pdf)
The project results show that UAV-based solutions not only save the field measuring work but also provide LiDAR-like accuracies with more visible details which can be admitted as evidence in court.
Links:
http://blog.pix4d.com/post/103641424926/uav-based-accident-and-crime-scene-investigation
