Subsea Positioning
Tracker 650 DVL Doppler Velocity Log
Tracker 650 - three transducer faces
The Tracker 650 is a 675 kHz Doppler velocity log that measures your ROV’s speed over the bottom, so the flight controller can hold station instead of drifting on the tether.
Three beams, one cable, no IMU of its own
Every figure here is from the specification table on this page. Hover or tap a number to trace it to the hardware.
- 01Velocity sensors3 beamsEach 70° down from horizontal. Three rather than four, and attitude comes from the vehicle.
- 02Ping frequency675 kHzPing repetition rate 5–20 Hz. Works from 50 cm up to 25–50 m above the target plane.
- 03Interface10/100 Mbps EthernetThe recommended interface. Serial is 3.3 V or 5 V TTL auto-sense, 115,200 8-N-1.
- 04Housing108 × 48 mmDiameter by height, rated to 300 m. 550 g in air, 135 g in water.
- 05Power10–30 V DC2.5 W averaged over 1 second, 5 W peak, through the combined Ethernet and power cable.
Every Tracker 650 DVL Configuration
The finished DVL, or the board-level OEM kit for building it into your own vehicle.
In position hold, Cerulean measure the ROV wandering slowly around a mean location with less than 1 m short-term circular error and less than 1 m/min long-term drift. What you get depends on control tuning, bottom type, vegetation cover, standoff height and the environment.
What differs between the configurations▾
| Specification | Tracker 650 DVL | OEM kit |
|---|---|---|
| Supplied as | Finished unit, ready to fit | OEM kit - board level, for your own build |
Everything else on this page is common to both configurations; which vehicle each one is cut for is on the cards above.
Key specifications19 rows▾
| Ping frequency | 675 kHz |
| Ping repetition rate | 5–20 Hz |
| Velocity sensors | 3 |
| Sensor down-angle from horizontal | 70° |
| Maximum operating height above target plane | 25–50 m |
| Minimum operating height | 50 cm |
| Maximum operating speed | 5 kts |
| Angular operating envelope | 0–10° off vertical |
| Maximum depth rating | 300 m |
| Device diameter | 108 mm |
| Device height | 48 mm |
| Weight in air | 550 g |
| Weight in water | 135 g |
| Input voltage | 10–30 V DC |
| Power, averaged over 1 second | 2.5 W |
| Power, peak | 5 W |
| Ethernet | 10/100 Mbps (recommended interface) |
| Serial | 3.3 V or 5 V TTL auto-sense, 115,200 8-N-1 |
| Built-in IMU | None - attitude comes from the vehicle |
Maximum operating height depends on tilt of the sensor head, flatness of the target plane, hardness of the target plane, vegetation cover and salinity - Cerulean list all five.
Minimum operating height assumes the sensor head is parallel to the target surface.
Maximum operating speed varies with height above the target plane.
Two Cerulean sources disagree on the angular operating envelope. The specification page above gives 0–10° off vertical; Cerulean’s own product page gives 0 to 20°. We publish the specification page’s figure, which is the conservative one. If the margin matters to your mounting, ask us and we will put the question to Cerulean.
Cerulean’s DVL-75 comparison page quotes a 20 m maximum standoff, a 0.3 m minimum and a single 10 Hz ping rate for the Tracker 650. Those conflict with the specification page on all three, and the same comparison page gives 5–20 Hz to the DVL-75 - the figure the specification page gives to this unit. We publish the specification page.
Published by Cerulean - specification page
What's in the box▾
Cerulean’s own packing list for this product.
What’s in the box
- Tracker 650 with its combined Ethernet and power wiring cable
- Blue Robotics RJ45 to JST GH adapter
The mounting bracket is a separate Cerulean product, not part of this packing list. Tell us what you are flying and we will put the right one on the quote.
Downloads▾
Three things a DVL does for a small ROV
Hold station without fighting the tether. Current and tether pull move an ROV constantly. With velocity over ground feeding ArduSub, the vehicle holds its own position while you work the camera, read a gauge or talk to the client. It is still there when you look back.
Navigate without surfacing. ArduSub integrates the Tracker 650’s position deltas into a dead-reckoned track. On a 435 m towed lake course, Cerulean measured 398 m of X displacement - the difference is rotation moving travel into the Y axis, because the tether was attached to the rear port side and pulled the vehicle about 20° off-axis - and report that the ROV’s dead-reckoning function agreed exactly with the GPS ground-truth for that test.
Fill the gaps in USBL tracking. A USBL gives you an absolute fix roughly once a second. A DVL gives you motion 5 to 20 times a second. Cerulean document that pairing the Tracker 650 with an Omnitrack enables USBL plus DVL sensor fusion on BlueROV2 systems, so you get a continuous track instead of a point jumping once a second.
It is not only for the seabed. Cerulean describe motion tracking relative to nearby surfaces such as the seabed, seawalls and barge bottoms, and the sensor orientation can be set to 6 orthogonal positions plus 4 rotations - so it can face forward at a quay wall or a hull rather than down.
Position-hold and dead-reckoning figures: Cerulean - what to expect. Omnitrack fusion, platform fit and the surfaces it will track: Cerulean - product overview. The 6 orthogonal orientations plus 4 rotations are from Cerulean’s Tracker 650 and DVL-75 comparison.
DVL or USBL: which does your ROV need?What the bottom does to the range
The maximum operating height is 25–50 m, and the spread is not vagueness. It is the bottom.
Cerulean list the variables as tilt of the sensor head, flatness of the target plane, hardness of the target plane, vegetation cover and salinity - and they publish their own results rather than a single flattering number. On a hard bottom such as Lake Superior they regularly reach 50 m; on a muck-bottom lake such as Lake Minnetonka they sometimes struggle past 30 m.
Vegetation shows up in the data as well as in the range. The unit reports a confidence value alongside every measurement, from 0 - which Cerulean gloss as don’t use - to 100. On Cerulean’s published test it sat between roughly 50 and 99, with the low values matching the weedy shallows. That number is visible to you in SonarView, which means you can watch the sensor losing faith in itself rather than guessing why the vehicle started wandering.
Practical consequence: if you work over soft silt or heavy weed, size your expectations at the lower end of that range. If you work over rock, sand, steel or a hull, the upper end is realistic.
The five variables and the 25–50 m figure: Cerulean - general specifications. The Lake Superior and Lake Minnetonka results and the confidence values are Cerulean describing their own testing, on what to expect.
What you drive it with
SonarView is free, runs on Windows, macOS and Linux, and runs in a browser when it is served from SonarLink - including as a BlueOS extension. You use it to configure the unit, watch the confidence and standoff values live, and fuse DVL motion with USBL fixes into one track. The unit also has its own built-in configuration web page, so you can set it up without installing anything.
For custom navigation work the message set is open: $DVKFC exposes raw data for your own Kalman filter, and $DVPDL and $DVPDX carry the position deltas.
Two things about that output are worth knowing before you build against it. The angle-delta fields are always zero - the unit has no IMU, so it has nothing to report there. And the roll and pitch estimates are not attitude: Cerulean are explicit that they are “based strictly on the range estimated of each beam, and thus will be noisy”, and that they exist to help you line the vehicle up against non-seabed items like ship hulls or seawalls. Read them as attitude and you will be debugging the wrong thing for an afternoon.
The roll and pitch caveat is Cerulean’s, on basic operating guidelines and hints.
Tracker 650 DVL, and what it produces
Photographs of the hardware - not renders.
The ArduSub quirks, in advance
Cerulean document these openly and we would rather you read them here than discover them on the boat. None of them is a fault in the DVL; all of them are ArduSub being particular.
- ArduSub accepts one global origin per power cycle, and only one. Cerulean’s wording: “ArduSub accepts one and only one global origin per session (a session is the time period during which the ROV is powered).” Until it has one, it will not hold position.
- There is a real trade-off in the automatic origin. The DVL can send a global origin of (0,0) each time it connects to the MAVLink REST server. That gets you position hold, but Cerulean are clear about what it costs: it “allows relative positioning not corresponding to the actual latitude and longitude”. Supply a real origin yourself instead and you get true coordinates - but nothing holds until you do.
- Sending NMEA GPS data to ArduSub disables DVL position hold and dead reckoning from then on. Cerulean’s own sentence: “If you send NMEA-formatted GPS position information to ArduSub, it will disable the ability thereafter to use position hold and dead reckoning based on DVL inputs.” The data can arrive from a GPS on the same network, or from a configuration utility whose NMEA output was never turned off. This one costs people an afternoon.
Getting this configured correctly the first time is most of the value of buying through a distributor who has done it before. Tell us the vehicle and we will walk you through the parameters.
All three are Cerulean’s, on global origin.
Common questions
Answers Cerulean publish, each linked back to the page it came from.
How well does position hold actually work?
The ROV wanders slowly around a mean position - Cerulean measure less than 1 m short-term circular error and less than 1 m/min long-term drift. Control tuning, bottom type, vegetation cover and standoff height all move that number. Source
How high above the bottom can it work?
Between 50 cm and 25–50 m, and the honest answer is that the top end depends on what the bottom is made of. Cerulean report regularly reaching 50 m over a hard bottom and sometimes struggling past 30 m over muck. Soft silt and heavy weed cost you range. Source
Will it work on my vehicle?
On a BlueROV2 it is plug-and-play with the flight controller. Any ArduSub or MAVLink2Rest vehicle works out of the box. Other platforms need what Cerulean call a light API integration. Source
Does it need calibrating?
No. Cerulean state plainly that the Tracker 650 does not require any calibration, because it has no IMU of its own - it uses the vehicle’s. That does mean your vehicle’s own sensors have to be properly calibrated for position tracking to be worth anything. Source
Can I use it with a USBL?
Yes, and it is the main reason to own both. A USBL updates about once a second; the Tracker 650 fills the gaps between fixes with velocity. Cerulean document that pairing it with an Omnitrack enables USBL plus DVL sensor fusion on BlueROV2 systems. Fusion with the ROV Locator on its own, for absolute position output, is not supported. Source
Can it track something other than the seabed?
Yes. Cerulean describe motion tracking relative to nearby surfaces such as the seabed, seawalls and barge bottoms, and the sensor orientation is configurable to 6 orthogonal positions plus 4 rotations, so the unit can face forward or sideways rather than down. Source
Why is it cheaper than other DVLs?
Mainly because it has no internal IMU and three velocity sensors rather than four. It measures velocity and leaves attitude and state estimation to the vehicle. For position hold on a small ROV that is the right trade. If you need a DVL that dead-reckons as a self-contained unit, ask us about the Water Linked A50 instead - we sell that too. Source
Request a Tracker 650 DVL quote
Tell us the vehicle and the water depth and we will confirm the exact part number - and say so if a different model suits the job better.
Anything you have added to your quote list is carried into this form automatically.