Dealing with LSPIV questions on the field: An approach for autonomous flood gauging using UAVs

In an era when flood phenomena intensify worldwide, the scarcity of proper and systematic flood flow measurements
has become a conundrum. As an answer, the non-intrusive Large-Scale Particle Image Velocimetry (LSPIV) method
has recently advanced to a contemporary gauging alternative, though several limitations in the field application pose
questions. To tackle relevant restrains, this study brings forth a new approach for LSPIV field applications and flood
gauging using lightweight unmanned aerial vehicles (UAV). In the core of the suggested approach lies a flexible yet
direct and accurate matching technique to define the water surface as reference plane, without the need for fixed
Ground Control Points (GCP) on the field. In addition, to address uncertainties relevant to apparatus movements that
occur from winds and gusts during field recordings, an error-removing process that utilises digital fictitious GCPs is
reported. The proposed techniques, implemented via a purpose-built application, are evaluated under various
recording conditions in both laboratory and field studies, with positive results. Overall, the granted autonomy, as a
result of the approach, provides applicability of the LSPIV method to practically any section of interest without the
need for construction or the presence of personnel in hazardous conditions, allowing for a safe, efficient, and low-cost
flood gauging alternative.