Mean Point Water Velocity refers to the velocity (speed and direction) of a single “point” of water (in this case, a volume of several square meters) averaged over time-scales associated with surface gravity waves. Water velocity is estimated using a sound pulse emitted from the sensor and measuring its Doppler Shift as it is received back by the acoustic receiver. The theory behind this measurement is that the sound pulse is reflected back to the instrument by reflecting off of particles in the water column. As the particles within the water column are assumed to move at the same velocity of the water, by measuring the velocity of the particle (via Doppler shift), one can obtain a measure of water velocity.
The following instrument classes include this data product:
- Single Point Velocity Meter (VELPT)