QYSEA Q-DVL — Doppler Velocity Log for FIFISH ROVs
Core Technology · Sonar Sensing
Q-DVL is QYSEA's fully self-developed sonar sensor module, built on the principles of the Doppler Shift effect. Fused with FIFISH ROVs and proprietary AI algorithms, it delivers centimetre-level station lock, collision avoidance and underwater navigation. Beyond integration, deep fusion enabled.
Sense · Hover · Avoid · Navigate
The sonar that lets a FIFISH hold its ground
Most ROVs drift the moment a current builds or the pilot looks away. Q-DVL changes that. By bouncing acoustic beams off the water column and the seabed and reading the Doppler shift in the returns, it measures exactly how fast — and in which direction — the ROV is moving, so the flight controller can cancel that drift and hold a precise position.
- Forward tri-beam Inline Q-DVL — vertical structures & forward collision avoidance
- Downward four-beam Q-DVL — flat seabeds, riverbeds and lakebeds
- 360° omnidirectional station lock hovering without dead angles
- Centimetre-level hovering accuracy · up to 100 m detection range
- Foundation for U-INS navigation, mission planning & bathymetric mapping
The problems Q-DVL was built to solve
Without a velocity reference underwater, an ROV is effectively flying blind in moving water. Q-DVL gives it a fixed sense of where it is and how it is moving.
🌊 Drift in Current
Open-loop ROVs lose position the instant flow builds. Q-DVL measures drift directly so the controller can null it out and hold station.
📍 No GPS Underwater
GPS doesn't penetrate water. Q-DVL provides the velocity reference that underwater inertial navigation needs to know where the ROV is.
💥 Collision Risk
In confined or low-visibility sites, contact damages structures and vehicles. Forward and downward ranging flags collision risk early.
📐 Unsteady Inspection
Blurred, shifting footage isn't measurable. A locked hover gives the camera and AI tools the steady platform they need.
Two sonar arrays, one precise position
A forward tri-beam unit and a downward four-beam unit work together — between them they cover vertical structures and flat terrain, reading velocity relative to both the water and the seabed.
Forward Inline Q-DVL — for vertical structures
QYSEA describes the Forward Inline Q-DVL as the world's first inline Q-DVL with a compact dimension. Three forward-facing beams are designed for vertical structures and complex subsea environments, enabling vertical U-INS navigation and forward collision avoidance where a downward-only sensor would have nothing to range against.
- Tri-beam array tuned for vertical surfaces and irregular structures
- Enables vertical U-INS along walls, curved surfaces and pilings
- Forward ranging underpins smart collision avoidance
- Available with an integrated Laser Scaler on selected configurations
Downward Q-DVL — for flat terrain
The Downward Q-DVL uses four beams aimed at the bottom, ideal for flat terrains such as seabeds, riverbeds and lakebeds. By tracking velocity relative to the bottom it achieves U-INS and mission planning, and feeds altitude data for distance and altitude lock. The self-developed sensors are adaptable across various FIFISH models.
- Four-beam bottom-tracking over seabeds, riverbeds and lakebeds
- Velocity relative to the bottom drives U-INS & mission planning
- Supplies the altitude reference for distance & altitude lock
- Self-developed sensors adaptable across various models
What deep fusion looks like underwater
Combined with proprietary AI algorithms, Q-DVL turns raw velocity data into three operator-ready behaviours — station lock, collision avoidance, and distance & altitude lock.
Station Lock Hovering
360° omnidirectional station lock without dead angles, with centimetre-level hovering accuracy and adaptive current resistance for full-range underwater stability.
Smart Collision Avoidance
The forward and downward units use distance data from both directions, combined with AI algorithms, to accurately identify collision risks — significantly enhancing operational safety.
Real-time Distance & Altitude Lock
With AI-algorithm assistance the ROV holds distance and altitude simultaneously across a 0.1 m–100 m height range — for consistent, efficient inspection passes.
Available on these FIFISH models
Q-DVL is a self-developed module adaptable across the FIFISH range — from the flagship industrial platform to compact portable ROVs. Explore the platforms that integrate it.
The flagship industrial platform — forward & downward Q-DVL feed station lock, QY-MT measurement and U-INS Plus autonomous navigation.
View the E-MASTER →Navigation-focused professional ROV — Q-DVL drives station lock, altitude tracking and bathymetric survey work.
View the W6 NAVI →A compact inspection platform where Q-DVL station lock steadies the vehicle for close-tolerance NDT and measurement.
View the X1 →The portable E-GO brings Q-DVL station lock to fast, single-operator deployments where stability still matters.
View the E-GO →Q-DVL configurations include Q-DVL Plus, Q-DVL Max, Forward Inline Q-DVL with Laser Scaler, Q-Cam D/L and Tri-directional Inline Q-DVL. Ask us which configuration suits your platform and mission.
See also: the industrial FIFISH platforms can integrate compatible third-party DVL and USBL positioning, such as Cerulean Sonar's positioning range.
What station lock unlocks in the field
A vehicle that holds its position turns difficult underwater work into repeatable, documentable operations.
Vertical Structure Inspection
Dam walls, quay walls, pilings and intake structures — the forward Inline Q-DVL enables vertical U-INS and steady inspection passes.
Close-Tolerance Measurement
A locked centimetre-level hover gives camera and AI measurement tools the stable platform they need for accurate, repeatable readings.
Hydrographic Survey
Downward bottom-tracking turns seabeds, riverbeds and reservoirs into 2D & 3D map deliverables during a normal dive.
Confined-Space Entry
Forward and downward ranging flags collision risk early — safer transits through tanks, culverts and pipelines.
Survey in Current
360° adaptive current resistance holds station where open-loop ROVs drift off target — offshore, in tidal flow and around structures.
Autonomous Missions
As the velocity reference behind U-INS, Q-DVL makes planned routes and repeatable POI passes possible without continuous piloting.
Q-DVL at a Glance
Key figures sourced directly from QYSEA. Detailed per-configuration specifications are confirmed on quotation.
Sensing & Performance ▾
| Principle | Doppler Shift effect (self-developed sonar) |
| Maximum Detection Range | 100 metres |
| Hovering Accuracy | Centimetre-level |
| Station Lock | 360° omnidirectional, no dead angles |
| Current Resistance | 360° omnidirectional adaptive |
| Altitude / Station-Lock Height Range | 0.1 m – 100 m |
Array Configuration ▾
| Forward Inline Q-DVL | Tri-beam — vertical structures & forward collision avoidance |
| Downward Q-DVL | Four-beam — flat terrain (seabeds, riverbeds, lakebeds) |
| Forward Macro Focus Distance | 10 cm |
| Configurations | Q-DVL Plus · Q-DVL Max · Forward Inline Q-DVL with Laser Scaler · Q-Cam D/L · Tri-directional Inline Q-DVL |
Capabilities ▾
| Station Lock Hovering | 360° omnidirectional, centimetre-level |
| Smart Collision Avoidance | Forward + downward ranging with AI algorithms |
| Distance & Altitude Lock | Simultaneous, AI-assisted |
| U-INS | Multi-dimensional underwater inertial navigation |
| Mission Planning | Route planning & customisable POI |
| Bathymetric Mapping | 2D & 3D map outputs (downward Q-DVL) |
Add Q-DVL to your FIFISH
Tell us which platform you operate and what you need to hold, avoid or navigate — we will recommend the right Q-DVL configuration and prepare a complete EUR quote.
Request a Quote — Q-DVL
Describe your platform and application and we will recommend the right Q-DVL configuration for your operations.