A system and method for determining positional order of vehicles across a threshold plane within a dynamic environment is provided. The system can include moving vehicles (e.g., boats) each having a GPS receiver. A reference object (e.g., an anchored boat) can have an image capturing device and a primary GPS receiver, and can be subject to movement induced by the dynamic environment. A fixed object having a known position (e.g., a government buoy) relative to the reference object define a threshold plane, which is subject to movement based on movement of the reference object. Photometric data gathered by the image capturing device and geospatial data gathered from the GPS receivers, the primary GPS receiver, and the fixed object is analyzed by a processor to determine a positional order at which each vehicle crossed the movable threshold plane.