On the afternoon of Valentine’s Day, 2 days out of Harbour Island Eleuthera, Bahamas, I had a good close encounter with a freighter. I say “good” for a couple reasons. From a Murphy’s Law perspective, so often when you have a close encounter with a freighter or cruise ship, it’s 3 AM, the wind is howling, there’s another freighter coming from the other direction at the same time, and on and on. In this instance, HJ was sailing herself at 5 knots in a favorable direction so I took some time to think through what I really should be doing in a close encounter.
Below decks, to the left of HJ’s navigation station (a.k.a., her nav station) is the electronics panel. I currently have her outfitted with 6 different electronics: primary GPS, back-up GPS, VHF radio (very high frequency) for short-distance communications (say closer than 30 miles), AIS, radar, and satellite weather/email/text. When in typical sailing mode I run the primary GPS, VHF radio and AIS. Radar is a power hog for a low-power boat like HJ so I only use it when in close quarters.
The AIS (Automatic Information System) unit is a relatively recent invention and an incredibly useful tool. Basically it’s a transponder—that is, it both transmits and receives—over VHF frequencies. When powered-up, my AIS unit is transmitting both static and dynamic information about Hazel James. Static information includes ship’s name, length and beam (width). Dynamic information includes our position, speed and course over ground (COG). Other ships’ AIS units are doing the same thing. Large ships and most all passenger vessels are required to run an AIS. Small vessels (such as HJ) are not, but it’s a darned good idea. Given my AIS unit ”knows” my dynamic information (position, course and speed), when it picks up another vessel’s signal it can determine the CPA and TCPA for our two vessels (Closest Point of Approach and Time of Closest Point of Approach)—as you can imagine, very important information to have. It’s hard to explain just how deceiving and confusing moving ships can be. Also, the AIS can “see” out to a distance of 24 miles. I can only physically see 3-8 miles depending on day/night, atmospheric conditions, etc.
With all that being said, in my every-thirty-minute checks of the horizon and AIS, I picked up a ship on the screen.
In the image above, we (HJ and I) are the black boat/triangle in the center of the screen. “N-UP” at the top of the screen indicates that we are running the unit with north being up (similar to the option on a car or phone GPS). You can tell our course over ground (COG) is roughly due east since that’s the way our boat is pointed on the screen. In this picture, the target ship currently has a range (distance) of about 4 nautical miles from us. One way to tell this is by the “12nm” in the bottom-left. That indicates that the max range of this setting of the AIS is 12 nautical miles. Therefore the concentric circles are each 4 nautical miles. Most importantly the CPA (closest point of approach) is currently 1.3 nautical miles—a comfortable distance, and the TCPA (time of CPA) is 17 minutes. Now keep in mind that I had “seen” the ship on AIS and visually much earlier. Also, not shown on this screen but visible elsewhere is the ship’s speed. In this case 16 knots, much faster than Hazel James’ 5 knots.
In climbing on deck for a visual, this is what I saw off my starboard (right) bow…
I could have left it at that and just enjoyed watching her pass safely off my bow. However, since I had some time on my hands, I decided to work on my radar skills. I’m good enough to get by with radar but always take the chance to practice in a controlled setting. Radar is a much older technology, it was invented in the 1930s.
About halfway up HJ’s mast is my radar transmitter and receiver, technically called the radome. In the image below (a cool camera shot if you don’t mind me saying so), the lower and wider unit with the blue base and the white top is the radome. In a related note, the narrower taller unit is a radar reflector to increase HJ’s radar image to other ships (technically called an RTE, radar target enhancer).
When transmitting, the radar is sending radio signals and receiving any echoes from those signals. There’s a lot more art involved with tuning and interpreting radar data as compared to AIS data. With the AIS you pretty much turn on and it runs. Radar takes a bit of work. However, if you see a ship/boat in the distance and don’t pick them up on AIS, they may not have AIS on board or may have it switched off. This happens a lot, as the high-seas are full of weirdness. Captains who don’t want to be seen for various reasons and military vessels don’t transmit AIS information. Conversely, radar doesn’t depend on the other boat to transmit anything.
There is an absolutely amazing story about the early days of radar in WWII. In 1939, the US military established the AWS (Aircraft Warning System) using “RADAR” (RAdio Detection and Ranging). On December 7th, 194 1 at 7 AM, radar operators from the Opana radar installation in Hawaii detected approaching aircraft at a range of 150 miles. After much back-and-forth between the operators and their command, they concluded it must be an incoming flight of B-17s—a tragic, tragic mistake. More on this here if you’d like to read.
Back to my story… I flipped on my radar and easily picked up the Seaspan Amazon on our radar screen. In the image below, the solid line is HJ’s direction of travel, again, we are in the middle of the scope. The blip to the right of the screen at a range of 4 nautical miles is the freighter. Interestingly, I put an EBL (electronic bearing line) on the screen to double check that the Seaspan Amazon would pass well in front of me. A “bearing” is another ship or target’s direction from your current position. The EBL is the dotted line below. I placed that line directly on top of the target ship’s blip several minutes earlier. You can see below that the ship has advanced in-front of the EBL indicating that it will pass in front of me (off my bow). Conversely, if the target had fallen behind my EBL, she’d pass off my stern (behind me). Finally—and you guessed it—if the target stays on the EBL, you’ve got trouble that you need to deal with…and quickly.
Back to the art of radar, the Seaspan Amazon is huge and it was an extremely calm day on the ocean. Radar gets a lot tougher when you’re trying to pick-up smaller vessels in rough seas and in rain, when the waves and precipitation are creating noise on the radar screen.
After all that, the Seaspan Amazon passed us a mile off our bow.
I said the Seaspan Amazon was huge? We’re talking 337 meters in length. That’s 1,100 feet or two-tenths of a mile long; 35 Hazel Jameses lined-up end-to-end would still be shorter than her. She can carry 115,000 tons of cargo. That is, she could carry 15,000 Hazel Jameses. The size is just mind boggling.
Although I don’t think there is any connection between Amazon.com and the Seaspan Amazon, the next time you order something online, take a moment to think about the size and shape of the global supply chain that is so much a part of everyday life and how stuff gets from here-to-there.
Thanks as always for reading and Hazel James out.