ROVL Channels (Autosync only; Operating Multiple Units in Proximity)

Mk II units equipped with Autosync can operate on one of two different channels (creatively desinated “Channel A” and “Channel B”), which allows two ROVL systems to operate in proximity without interfering with each other. This is accomplished with time-division multiplexing referenced to GPS time. The channel setting is persisted in non-volatile memory for both transmitters and receivers. The system can be set up so one receiver can switch back and forth between monitoring two transmitters, or two receivers can each monitor their own transmitter. This feature does not degrade the normal 1 Hz update rate. See the “I” command to learn how to switch channels.

Some example usage scenarios for units in proximity:

• Two ROVs, each with an ROV transmitter, operating side-by-side with two operators, each able to see their own ROV’s position (no user software development is needed for this).

• One ROV with a transmitter, one diver with a transmitter, and an operator who can select which one to monitor, or simultaneous position display of the ROV and diver.

• An untethered ROV with an ROVL receiver and transmitter both installed. The ROV could use its receiver to navigate to home (or other location where the transmitter is sited), and the topside crew could monitor the position of the ROV using their own receiver (some user software development is needed for ROV guidance).

• A tethered ROV in a challenging magnetic environment could have both an ROVL transmitter and an ROVL receiver installed. The topside station could monitor the position of the ROV. The ROV could send relative tracking angles and pitch/roll from its receiver back to the topside station through the tether. With these pieces of information, the topside station would be able to compute the heading of the ROV as well as its position, allowing navigation even without an ROV-mounted compass (some user software development needed for fusing the outputs of the two systems and converting them to a heading).

Note: ROVL units without autosync (including all Mk I and Mk III units) operate on both channels A and B, although they do not belong to either channel. Therefore, units without autosync will interfere with the operation of autosync units, and vice versa.

Note: The point of separate channels is to make the transmitters on the opposite channel invisible. Thus, if you accidentally set your transmitter to a channel other than what your receiver is set to (or vice versa), your system will seem not to work, and it will appear to be broken. The solution is to set the receiver to the channel the transmitter is using. To prevent accidental channel switching while familiarizing yourself with the system, CeruleanTracker does not have a channel-switch button. You will need to type the channel-switch command into the command input box on the ROVL Command Window.

Note: ROVL units with autosync are shipped set to channel A.

Note: To set the channel on the transmitter, it will need to be connected to a serial port and a terminal program (CeruleanTracker software can be used for the terminal program). Once the channel is set, the serial connection is no longer needed. Remember the autosync transmitters operate at 9600 baud to emulate GPS units.

Mk II Autosync units with receiver software after August 9, 2021, can be set to receive on both ROVL channels simultaneously, allowing you to track up to two transmitters simultaneously. When in this mode a $USRTH message is sent for each channel once per second. The “Channel” field in the message identifies which channel produced the data. See the “I” command to learn how to activate this mode.

Note: See the CeruleanTracker manual for information on how CeruleanTracker handles dual-channel operation.