Targetless Digital Surface Modeling from UAV imagery
iWitnessPRO offers a fast, reliable, flexible and cost-effective means to map traffic accidents from photographs captured from a UAV/drone. A case study is presented of an incident mapped by police using a DJI Inspire 1.
The accident occurred when a pick-up truck ran a red light and was hit mid-intersection by a SUV that was proceeding on a green light. The collision caused the truck to veer on to the side where it struck and injured a pedestrian.
The first Investigators on the scene marked and painted vehicle locations on the roadway, tire marks and physical evidence relevant to the vehicle collision. This prepping of the scene was carried out while the Emergency Medical Technicians treated and transported the victims to the hospital.
A forensic collision reconstruction expert then used a police drone to record aerial photography of the scene, the on-site preparation time for the drone deployment being only 15 minutes. The data processing for the automated photogrammetric mapping and documentation of the accident scene was then carried out, with all necessary surveying data being produced within 30 minutes. Diagramming was then performed after the resulting 3D point cloud, that was later imported into a CAD system.
In comparison to traditional accident scene surveying and documentation methods, the use of the UAV-photogrammetry saved a significant amount of time both on scene and back in the office. The UAV approach is estimated to be, on average, about three times faster on scene than operations with total stations and conventional tapes.
The associated disruption to commerce caused by road closures is thus significantly reduced in the UAV-photogrammetry approach, with the required accuracy of measurement of a few centimeters being readily achieved. The complementary high reliability of multi-image photogrammetry, coupled with the fact that the photography offers an irrefutable, permanent visual and metric record is a further compelling advantage of UAV-photogrammetry for accident scene mapping.
|3D Project Example: Dense Surface Matching of Vehicle Crush|
|DSM Project Example: Fire Investigators & Mapping Wildland Fires|
iWitnessPRO – Red Codes & Signalized Targets
iWitnessPRO allows the user to achieve accurate, fully automatic measurement of targeted feature points through the use of coded target technology, while retaining all the measurement flexibility contained within the manual and operator assisted measurement functions of iWitness.
As with iWitness, iWitnessPRO can be used with any digital camera, though the automated functions and measurement accuracy are optimized when digital SLR cameras are employed. Supplied with iWitnessPRO are the necessary re-usable red retroreflective coded targets. Coded targets can be distributed throughout the measurement volume whereas feature point targets, triplet offset targets, and strip tape targets are optionally used to mark specific points of interest, which do not need referencing by the operator.
The following vehicle mapping was conducted in cooperation with the Washington State Patrol. An exemplar Chevy Impala was imaged with iWitnessPRO coded targets and then facet-form polyline traced, Additionally, the same make/model/year vehicle involved in a crash that impacted a tree and caught on fire, was also 3D modeled, using iWitnessPRO. The exemplar with the ‘crash & burn’ vehicles were merged in iWitnessPRO for dimensional comparison in CAD.