All USBL systems calculate position by measuring the range and bearing from a vessel-mounted transceiver to an acoustic transponder fitted to a moving target or placed on the seabed.
Here we offer five top tips on how to get the best out of your USBL systems and make sure your tracking performance in shallow water is trouble free. You can also watch our quick video, below.
Top tip #1
Consider where to deploy your transceiver. Is it on a rigid pole? Mounting your transceiver on a rigid pole will improve the performance of your system in any depth of water, not just shallow water.
Top tip #2
Make sure there’s enough distance between your vessel hull and your transceiver. This will reduce the amount of background noise from your vessel that interferes with your USBL positioning. Also, consider where on your vessel to put your transceiver. Try to avoid deploying it near the propeller because the noise and aeration from it will affect system performance.
Micro-Ranger 2 is already optimised for shallow water tracking. However, if you’re tracking with Mini-Ranger 2 at an elevation angle above 30 degrees, make sure you have depth aiding turned on at the beacon you’re tracking. This is easy to do. Just go to the beacon table in your Micro-Ranger 2 software, click on the sensor tab and then select the sensor from the depth aiding drop down. It’s also important to turn off depth aiding when you’re tracking underneath the vessel.
Top tip #3
Shallow water environments are by their very nature highly variable. Consider the environment you’re working in and pick the system setting that suits it best in order to optimise performance. For example, if you’re working in a noisy environment, such as waves or rain, you might want to set your beacon power levels to high. This will aid the acoustics to cut through that background noise and make sure they’re detected.
If you’re working in very calm water or near structures or walls of docks, for example, this may result in echoes and reverberation. In this environment, it’s best to set your power levels to ultra-low. This will avoid the echoes giving you false detections, so you’ll get much more accurate tracking. You can change a beacon power by opening the beacons table, then clicking on the advanced settings tab and selecting the power level you want from the drop down menu.
Top tip #4
If you’re always tracking a target at the stern of your vessel at high elevation, such as a tow fish, you might want to tilt your transceiver head towards your target. This will increase sensitivity in that direction and improve performance. However, seek advice because if this is implemented poorly it may result in increased background noise and reverberation. You can also use a 30 degree adaptor flange to point the transceiver back to the target.
Remember, Micro-Ranger 2 is already optimised for shallow water tracking, so tilting the head is not required. And, as we outlined in tip #1, care should be taken on the position of the transceiver to make sure you don’t introduce any more internal noise into the system. Also, if you tilt the transceiver head, remember to turn the depth aiding off.
Top tip #5
The type of beacon you use can be critical. Omni-directional beacons are used extensively in shallow water tracking and their performance can be optimised in the way we’ve described above. However, sometimes a directional beacon may be your best option, especially in high elevation high noise acoustic environments. These beacons focus their acoustic energy to make them much more detectable, giving you more robust tracking in those situations.
We hope these tips have been useful. If you have any questions, please don’t hesitate to get in touch. We’re here to help you get the best out of your Sonardyne USBL system.