Basic Operating Guidelines and Hints

The Tracker 650 is optimized for use on an ROV. When using in other scenarios also consider the guidelines below in light of your own scenarios.

The Tracker 650 should be operated so it is as close to level as possible when moving. Most ROVs have a flight controller that holds it level during flight. If you fly your ROV in a tilted orientation, then you should adjust the DVL orientation to fly level.

The ROV should be ballasted so it floats exactly level when it is disarmed.

The Tracker 650 reports a "roll" and "pitch" estimate in the $DVPDX message. Not to be confused with actual roll and pitch, these are based strictly on the range estimated of each beam, and thus will be noisy if the seabed has clutter or uneven vegetation or slopes. The intent of the roll and pitch estimates are for use when the DVL is mounted in a non-standard way (e.g., pointing forward) to help you line up your vehicle with non-seabed items like ship hulls or seawalls. So 0,0 roll and pitch means the DVL sensor is parallel to some surface which may be at arbitrary orientation.

We supply a user interface for the Tracker 650 called CeruleanTracker. It does not need to be running for the Tracker 650 to work. You can use it to set options or send positions (see below).

The Tracker 650 is designed to work with MAVLink and BlueOS to do position hold and dead-reckoning navigation in conjunction with QGroundControl (QGC), ArduSub, and BlueOS using an interface called MAVLink (MAVLink is the interface to ArduSub). There are no plug-ins required to make the Tracker 650 work with newer versions of BlueOS. You should be aware of a few quirks:

  1. ArduSub is the part of the system that combines the Tracker 650 odometry with the ArduSub's inertial measurement unit (IMU) to provide position tracking. In order to get good position tracking you must make sure the basic sensors are properly calibrated. The Tracker 650 does not require any calibration.

  2. You don't need a BlueOS extension to use the DVL. You do, however, need to tell ArduSub that a DVL will be sending it messages.

  3. When ArduSub is powered up it "thinks" it is located at latitude 0, longitude 0, a point somewhere off the west coast of Africa. If you are using QGC, the map overlay is blank here.

  4. Before ArduSub will do position hold, it must be given a Global Origin. The Global Origin tells ArduSub where it is located in the world.

  5. The Tracker 650 can optionally send a Global Origin message of (0,0) to ArduSub while everyone is waking up. This location is that same spot off the coast of Africa. If you set the Tracker 650 to automatically send the Global Origin, then position hold will always work and you can do relative tracking of the ROV position in QGC. This does make it more difficult for novices to get the real-world ROV position to show correctly in QGC. The Tracker 650 is shipped with this feature turned off. Rule of thumb: if you only care about position hold, turn this option ON. If you want to see the true lat/lon posiiton of the ROV on the QGC map, turn this option OFF and figure out how to get the the starting position of the ROV to ArduSub.

  6. ArduSub can only be told its Global Origin one time per power cycle. The Tracker 650 option to send a global origin defaults to off, because if you have a different way to set the true latitude/longitude position of the ROV, it won't work if the Tracker 650 gets there first with its (0,0) message.

  7. The Tracker 650 does accept a command called SET-POSITION that can pass the Tracker 650 a position in DD, DDM, OR DMS format, and the Tracker 650 will pass this along to the ROV using a Global Origin message. So, if you are able to send commands to the DVL, you can leave the default Global Origin message turned off and send the true GPS position when you are ready.

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