1. Introduction

The Geolux VX60 Surface Velocity Radar uses advanced radar technology to accurately measure surface flow velocity without contact with the water. The sensor operates without touching the water surface, so the installation is quick and simple. The instrument is mounted above the water, and only minimal maintenance is required.

The VX60 operates by transmitting a modulated electromagnetic wave in the 60 GHz frequency range (V-band). The transmitted wave reflects from the moving water surface and returns to the sensor. The instrument measures the frequency shift of the reflected signal, which is caused both by the motion of the water and the radar wave modulation. This measurement method is called Frequency-Modulated Continuous Wave (FMCW) radar. Using advanced signal processing techniques, the VX60 analyzes the returned radar signal to determine the distance to the reflecting surface and the velocity of the moving surface. Based on this information, the instrument creates a range-Doppler map, which shows the velocity of objects at different distances from the sensor.

Unlike simple Doppler radars that transmit a non-modulated signal and measure only a single Doppler shift, FMCW radar can distinguish between moving objects at different distances. This is especially important in surface velocity monitoring applications. For example, during rainfall, the VX60 can clearly distinguish between reflections from raindrops and reflections from the river surface. Conventional Doppler radars cannot fundamentally separate these signals and must rely on heuristic filtering algorithms to reduce rain effects.

The VX60 measures surface velocities from 0.020 m/s to 16.000 m/s, with a resolution of 0.001 m/s.

The instrument also includes an integrated tilt sensor which continuously measures the mounting angle of the device, and the measured surface velocity is automatically corrected using cosine compensation based on the detected tilt angle.