ADCP Current Profiler Velocity Calculator

Oceanography & estuarine hydraulics: Model acoustic Doppler frequency shift, radial and orthogonal velocity precision, bin size, and depth profiling limits.

Transducer & Profile Configuration

Acoustic Frequency f₀ (kHz): Nominal operating carrier

Beam Convex Angle θ (°): Janus beam inclination from vertical

Depth Cell / Bin Size Δz (m): Vertical range gate discretization

Pings per Ensemble N: Ensemble ping averaging count

Expected Water Velocity u (m/s): Horizontal current magnitude

Speed of Sound c (m/s): Seawater sound velocity

Acoustic Doppler & Precision Analysis

Doppler Frequency Shift (Δf)

Horizontal Velocity Std Dev (σ_u)

Vertical Velocity Std Dev (σ_w)

σ_w = σ_r / (2 · cos θ · √N)

Approx. Max Profiling Range

Acoustic Wavelength (λ)

λ = c / f₀

Ambiguity Velocity (v_amb)

Phase wrap limit

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Frequently Asked Questions

What is the Janus beam configuration in an ADCP?

The Janus configuration uses 4 beams mounted at equal azimuth angles (90° apart) inclined outward from the vertical axis by 20° or 25°. Opposing beam pairs (Beam 1 & 2 for pitch/u, Beam 3 & 4 for roll/v) cancel vertical velocity variations during horizontal velocity calculation.

Why does increasing depth cell (bin) size reduce velocity error?

A larger depth cell allows a longer acoustic pulse or correlation lag, transmitting more energy into the water volume. The radial velocity precision scales inversely with bin size (σ_r ∝ 1/Δz).

What causes ADCP ringing and the blanking distance?

After transmitting an acoustic ping, the ceramic transducer piezo-element vibrates (rings) for a brief interval. The instrument cannot receive backscatter until ringing dies down. This dead zone immediately in front of the transducer is called the blanking distance.