Using Unmanned Aircraft Systems for Crash Reconstructions During Suboptimal Conditions

The Texas Department of Transportation (TxDOT) has a strategic interest in using unmanned aircraft systems (UASs) to support a variety of initiatives, including traffic incident management. TxDOT is interested in identifying and documenting UAS uses to determine to what degree UASs can be used to streamline the process to clear and document fatal crash scenes. Environmental conditions such as wind, rain, and limited ambient light affect both UAS flight operations and the quality of the data collected. Fatal crashes can occur at any time, which means that UAS flights might need to occur during conditions that are less than optimal. To better understand the feasibility of using UASs under these conditions, this research documented key challenges and developed and tested procedures for data collection and processing. The research included reviewing historical crash data trends in Texas to establish correlations with environmental factors, simulating the effect of environmental factors on the quality of data collected with UASs, performing field tests of UAS-based crash data collection activities under a variety of conditions, and developing recommendations for updates of the TxDOT Unmanned Aircraft System (UAS) Flight Operations and User's Manual. Evaluated environmental factors include impact of wind speed and direction on UAS flight operations, impact of aerial imaging network design on 3D crash scene reconstructions using commercial structure-from-motion (SfM) software, impact of ambient lighting and low visibility on UAS-SfM reconstructions, self-calibration versus preflight calibration procedures for consumer-grade nonmetric digital RGB cameras, impact of suboptimal conditions on visual image quality, and impact of camera properties on UAS image quality to guide crash scene imaging.