Marine Research Station

Doppler Velocity Log

Acoustic Doppler sensing for underwater velocity estimation — dead reckoning's best friend.

  • #acoustics
  • #DVL
  • #dead-reckoning
  • #underwater

What is a DVL?

A Doppler Velocity Log (DVL) is an acoustic sensor that measures the velocity of an underwater vehicle relative to the seafloor (or water column) by exploiting the Doppler shift of reflected acoustic pulses.

Operating principle

Four acoustic beams are transmitted at oblique angles. Each beam’s Doppler shift fdf_d relates to the radial velocity component vrv_r as:

fd=2vrf0cf_d = \frac{2 v_r f_0}{c}

where f0f_0 is the transmit frequency and c≈1500 m/sc \approx 1500\ \mathrm{m/s} is the speed of sound in seawater.

Combining the four beams (Janus configuration) resolves the 3-D velocity vector [vx, vy, vz][v_x,\ v_y,\ v_z] in the sensor frame.

Dead reckoning with DVL + IMU

Integrating DVL velocity with an IMU attitude estimate gives a Dead Reckoning (DR) position:

pk=pk−1+Rk−1b→n vkb Δt\mathbf{p}_{k} = \mathbf{p}_{k-1} + \mathbf{R}_{k-1}^{b \to n}\, \mathbf{v}^b_k \,\Delta t

Error accumulates over time → typically fused with USBL or LBL fixes.

See also