West Vancouver Station 1 of the Royal Canadian Marine Search and Rescue (RCM-SAR) has successfully completed the implementation of data marker buoy tracking using AIS (Automatic Identification System). Deploying a DMB is critical for successful marine searches. Is using AIS technology a significant improvement? Let’s take a closer look at the goals and details of the project along with the benefits of real-time DMB tracking using AIS.
Deploying a DMB into the water at the start point of most searches (datum) is a key tool for monitoring drift and guiding search patterns. On the British Columbia coast, marine searches are overseen by the Joint Rescue Coordination Centre (JRCC). JRCC has other tools at its disposal to estimate drift but also relies on SAR vessels to relay DMB location and drift information to better evaluate on-scene conditions.
For many years the MetOcean Novatech RF-700C1 VHF radio beacon and Xenon flasher combo has been used by RCM-SAR crews along with a float collar and skirt as a DMB. On the coast we use VHF channel 15 to detect pings from the DMB using a Taiyo radio direction finder (RDF). These pings are used to find a hard-to-locate DMB. Cost of the Novatech beacon is approximately $2,000.
The Novatech beacon is a rugged and durable product with a rated depth of 1968 feet. It does however have some disadvantages when used for marine search and rescue, such as:
- A RDF must be used for tracking, which is a slow process
- Limited range, particularly during the day
- Easy to lose in rough conditions
- No real-time tracking
- Expensive to purchase for a volunteer organization
MetOcean specifies the range to be 4-8 nautical miles (nm). However, this is the best case scenario if using a highly elevated receiving antenna on a large ship or airplane. Experience has shown that we lose pings from the unit 0.3-1 mile away using RDF antennas on SAR vessels. At night the strobe increases the practical range to two to three nm. In rough seas it is hard to find the DMB post search. This increases risks for crews and also the overall search costs.
Investigating AIS Tracking
Alistair Duncan from RCM-SAR’s West Vancouver Station got wind of a pioneering effort by Rob Roe of the Sooke Station. Rob had apparently tried to prototype a DMB that transmitted AIS tracking data on standard AIS channels 87B and 88B. Rob went to register a Maritime Mobile Service Identity (MMSI) number for the AIS transmitter but was declined by Industry Canada. Their position was that it was not a vessel and it might confuse other ships.
Not to be dissuaded, Alistair investigated other options. He found the vmsTRACK, which is an asset tracking product by Weatherdock of Nürnberg, Germany. It can be programmed to non-standard AIS channels. The vmsTRACK is a special version of Weatherdock’s easyRESCUE series of personal locator beacons also known as an AIS search and rescue transponder (AIS-SART). It is also waterproof and it floats.
This led Station 1 to evaluate it as a new method of DMB tracking. Alistair, our Maintenance Officer Boudewijn Neijens and I kicked off the AIS DMB project with the following goals:
- Reduced cost of a DMB
- Increased range
- Real-time tracking and easier retrieval
- Utilize existing equipment where possible
- Private AIS transmission not receivable by other vessels
Station 1’s vessel Craig Rae Spirit has three older E90w Hybrid Touch displays networked together. We also have a Raymarine Class B AIS 650 transceiver to send our position to other ships and to receive and display nearby AIS targets. After consultation with the local Weatherdock dealer — Startech Marine of North Vancouver — we ordered both the vmsTRACK A130 ($700) and easyRX2S receiver ($900). Both the transmitter and receiver can be programmed to use VHF channel 15 or other channels depending on the application. The vmsTRACK we tested has since been succeeded by the vmsTRACK Pro A193-CS. This version has minor upgrades and has been ordered for our second DMB.
Startech Marine came to our Station to install the receiver and assist with the programming and testing of the vmsTRACK unit. Our first attempt was to connect the Easy RX2S AIS receiver into a NMEA 0183 input on one of our Raymarine displays. A conflict with the Raymarine AIS650 caused us to rethink this strategy. The multi-function displays do not reconcile two different AIS sources feeding in data on different inputs. Understandably, nobody would usually ever need to set things up this way.
Our second attempt was to use the built-in NMEA multiplexer in the easyRX2S to combine the Raymarine 650’s AIS ship target data along with the AIS data from the vmsTRACK. We disconnected the SeaTalkng cable from the Raymarine unit and fed the data via NMEA 0183 directly into the Weatherdock receiver. The receiver was then connected to one of the Raymarine displays. This display then re-broadcasts the data to the other displays on the network.
The setup shown in the diagram worked great at the dock so we progressed to some real-world testing. The next step was to re-design the DMB to hold the VMS Track and keep the antenna pointing straight up.
What is great about this new approach is that all other ships — other than RCM-SAR vessels — will not see our DMB’s AIS data. It remains hidden from view for everyone else. This alleviates Industry Canada’s concern about confusion. It also gets around having to register an actual MMSI number for a device that is not a ship. The tracker also leaves less of a footprint on VHF channel 15. This is because it is only sending digital micro-bursts of data, not the longer bursts of analog static that the Novatech beacon transmits.
You can see on the target list in the photo we have named the DMB RCMSAR DMB01. The “01” representing our station ID. The second DMB for our new vessel SAR1B, will have a B appended to the name. We also programmed the AIS destination field to be “West Vancouver” for further identification. Note that it will be really important for all RCM-SAR stations to follow a standard naming convention.
One of the great benefits is that you can now see the course over ground and speed over ground of the DMB in real-time. You also have access to the position of the DMB at all times, assuming you are in range. An additional benefit is that the Weatherdock AIS receiver includes an SD card slot which allows DMB drift data to be stored and reviewed back at base.
Fixed Position Range Testing
The vmsTRACK can be programmed to send out a signal at a pre-determined frequency. Station 1 presently has set this to 1 minute which is frequent enough for tracking while preserving battery life. With further testing we might change this setting to every 10 seconds to speed up initial signal acquisition time. Battery life at 1 minute intervals is estimated at 48 hours.
Our first test was to put just the tracker (no DMB) on Grebe Islet about 6 feet up (so it didn’t wash away). We then headed toward UBC. At about three nm we lost it on the AIS target list. We then backtracked and it took awhile to reacquire it. We went to within two nm before we found it again. This looked promising but it was not a floating test. It was guessed that the signal might be blocked or reflected by the island. Next we needed a DMB prototype we could drop in the water.
Weatherdock sells both a charging cradle ($60) — which we have permanently installed in our boat — and a version which is just a non-charging holder ($20). Boudewijn attached this holder to an ABS pipe along with an ACR firefly strobe, the MetOcean skirt, a float (under the skirt) and zincs acting as counter weights at the bottom. This design has now been updated but it served the purpose of our first floating range testing.
Floating Range Testing
The prototype DMB was deployed in open water in Howe Sound. Conditions were one foot chop and some wind, fairly normal summer conditions. We lost the signal somewhere around 5.3 nm from the DMB, and then returned slowly to reacquire the signal again around 5.3 – 5.2 nm. Curiously the DMB first showed up for a couple of minutes without any identification other than its MMSI number (preset from factory). The AIS transmits every minute, so the data is quite accurate. We checked the lat/long position indicated by the AIS when we recovered the unit. The reading was 100% in line with the vessel’s own GPS.
Final DMB Design
After the successful test of our DMB prototype Boudewijn had some concerns. He felt there wasn’t enough protection for the tracker and that because the cradle pushed the centre of gravity outward it was causing an imbalance.
Crafty as always, Boudewijn refined the design which removed the cradle and replaced it with a piece of flattened ABS pipe covered in reflective material. This balances the DMB much better and provides better impact protection.
Using AIS to track a SAR DMB is a huge leap forward and is long overdue. I’m extremely excited to share Station 1’s results and I hope other Stations move quickly to change out their DMBs to take advantage of AIS tracking technology. I can also see benefits of using this approach for oil spill tracking on the coast. All of our project goals have been achieved and the benefits are numerous.
We now have a more than five-fold increase in range which will make retrieval quicker and easier with substantial fuel savings. The overall cost of the DMB for each Station is about the same for the first DMB purchase — if you factor in the needed receiver. The savings come when you lose or replace the older Novatech beacon- based DMB, which costs nearly twice as much as fabricating a vmsTRACK version. Monitoring the DMB in real time and being able to instantly provide updates to JRCC might just be the critical factor that finds the next missing person in time!
– Safe Boating –
Note: This article was also published in RCM-SAR’s Compass Newsletter (Sept 2016)