These days the crew of exploration vessel, Baseline Explorer, and of GlobalSubDive is busy readying for the next mission that will commence next month.
It’s still too early to reveal much about this exciting expedition, but you can be sure it’s going to be an interesting endeavor, and for sure we will be bringing you much more information and findings as we progress further and as we are in a position to lift the veil a bit more on what this will all be about.
This week “The Nelson pole”, our new submersible communications and tracking pole, was installed on GlobalSubDive’s exploration vessel, Baseline Explorer. A lot of blood and sweat went into this. Baseline Explorer is well equipped to handle our upcoming expeditions.
The pole can be utilized with a number of communication devices and as mentioned it is also used to pinpoint the position of the submarines when they are below the surface.
Pinpointing the location of the submarines is done using usbl. Here’s what that is:
USBL (ultra-short baseline, also sometimes known as SSBL for super short base line) is a method of underwater acoustic positioning. A complete USBL system consists of a transceiver, which is mounted on a pole under a ship, and a transponder or responder on the seafloor, a towfish, or on an ROV or in our case submarines. A computer, or “topside unit”, is used to calculate a position from the ranges and bearings measured by the transceiver.
An acoustic pulse is transmitted by the transceiver and detected by the subsea transponder, which replies with its own acoustic pulse. This return pulse is detected by the shipboard transceiver. The time from the transmission of the initial acoustic pulse until the reply is detected is measured by the USBL system and is converted into a range.
To calculate a subsea position, the USBL calculates both a range and an angle from the transceiver to the subsea beacon. Angles are measured by the transceiver, which contains an array of transducers. The transceiver head normally contains three or more transducers separated by a baseline of 10 cm or less. A method called “phase-differencing” within this transducer array is used to calculate the angle to the subsea transponder.
USBLs have also begun to find use in “inverted” (iUSBL) configurations, with the transceiver mounted on an autonomous underwater vehicle, and the transponder on the target. In this case, the “topside” processing happens inside the vehicle to allow it to locate the transponder for applications such as automatic docking and target tracking.
Stay tuned with us to learn more a the story on the upcoming expeditions unfolds.