Balloon-borne spectrum–polarization imaging for river surface velocimetry under extreme conditions

River discharge measurement is very important for river hydrology, river dynamics, etc. However, under extreme conditions, the river always has the characteristics of tremendous variation of flow discharge, high sediment concentration, large quantity of floating debris, and so on, which make the traditional river discharge measurement methods and instruments difficult to implement. To solve this problem, this note presents a novel scheme for river surface velocimetry based on spectrum–polarization imaging (that is, imaging the river surface using both spectrum and polarization features) and low-altitude telemetry technology. At first, to improve the accuracy of river surface dim targets detection and motion vector estimation, an imaging method based on near-infrared (NIR) spectrum–polarization is proposed for river surface monitoring. Then, to solve the contradiction between the large field of view and the shooting angle of shore-based large-scale particle image velocimetry (LSPIV) system, a balloon-borne low-altitude telemetry system with a self-stabilized servo platform is designed, which records the large-scale river surface images at an approximately vertical angle to the flow surface. This scheme will play an active promoting role in the development and improvement of wild river discharge measurement under extreme conditions.