What is a DVL and how does it work?

What is a DVL?

A Doppler Velocity Logger (DVL) is an instrument that measures the velocity (speed and direction) of an underwater vehicle relative to the sea bottom. They can be used in a broad range of applications, including underwater navigation, surveying and oceanographic research.

How does a DVL work?

A DVL works by using the Doppler effect, which is the change in frequency of a wave due to the relative motion between the source of the wave and the observer. DVLs transmit a series of sound waves towards the sea bottom and then measure the frequency shift of the reflected echoes. The Doppler shift is directly proportional to the relative velocity between the vehicle and sea bottom.

Typically, a DVL has 4 transducers which emit sound beams in 4 different directions, by comparing the Doppler shift echoes from each transducer, the DVL can calculate the vehicle’s speed and direction of travel. As the vehicle moves, the frequency of the sound waves is shifted due to the Doppler effect, the DVL then measures the amount of this shift and calculates the velocity of the vehicle relative to the sea floor. By combining the measurements from all 4 transducers, the DVL can calculate the velocity of the vehicle in 3 dimensions (forward/backward, left/right and up/down).

A DVL is typically mounted to the bottom of an underwater vehicle such as an ROV (remotely operated vehicle) or an AUV (autonomous underwater vehicle).

For a stand-alone DVL, the Syrinx DVL is available in two frequencies; 400kHz or 600kHz which offers the altitude performance of a 1200kHz DVL with the precision of a 300kHz. For a combined INS and DVL solution, we also offer a family of hybrid navigators; the SPRINT-Nav integrates a full Syrinx 400kHz or 600kHz DVL, pressure sensor and a SPRINT acoustically aided INS, this system can support complex survey and navigation missions using ROVs (Remotely Operated Vehicle) and AUVs (Autonomous Underwater Vehicle). Another member of our family of hybrid navigators is the SPRINT-Nav Mini which has 3 ROV instruments in one; a 500kHz Syrinx -derived DVL, hybrid AHRS and depth sensor, this is pre-calibrated making it quick to mobilise.