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Opening Day on San Francisco Bay April 29th! | Automatic Identification System (AIS)

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  • Phelps Hobart
    BoatingSF.com has a great monthly newsletter of interest to all mariners not just boaters. Some of the graphics may be missing; if so please visit the website.
    Message 1 of 1 , Apr 26, 2007
      BoatingSF.com has a great monthly newsletter of interest to all mariners not just boaters.
      Some of the graphics may be missing; if so please visit the website.
      Anchors Aweigh for a day on the Bay!
      Phelps Hobart
      BoatingSF.com San Francico Bay Boating Newsletter

      Fellow San Francisco Bay Enthusiasts,

      This month marks the one-year anniversary of the launch of our real-time ship tracking page, using information received from the AIS system. It quickly became the most popular page on the site. In this issue of the newsletter we'll present some interesting findings from this year of ship data, and some photos of the commercial ships on the bay.

      Before we dive into AIS, though, there's two upcoming events we wanted to be sure you were aware of:

      • Opening Day on the Bay is Sunday, April 29. There's no better excuse to get out on the Bay. If you don't have a boat, or a friend's boat you can hop on, check out the many companies offering scheduled cruises on sail or power boats. It's a great day for boatwatching.
      • The KFOG KaBoom on May 12 is a concert that includes a great fireworks show off the east coast of San Francisco, just south of the Bay Bridge. In some ways, it's even better than the fourth of July. See the links in the previous item if you're looking for a cruise to join.

      What is AIS?

      All commercial ships over 60 feet are required to carry AIS (Automatic Identification System) transponders, which send frequent ship status messages on a VHF channel. You can buy a receiver that converts the VHF signal to a serial data stream for about $200, which you can feed into your PC and decode with software such as ShipPlotter.

      In our case, there's quite a bit more to it, as we have to stream data from the receiver to our server, decode the messages on the server, and store the information in a database. The web pages that display the ship positions extract information from the database and animate it using a Flash program.

      We began with only one receiver, and when the Internet connection at that location failed, the data stopped updating. We now have two receivers, providing slighly increased coverage and significantly improved reliability.

      We're indebted to Slater Marinoff & Co, a great furniture store in Berkeley (which is owned by my sister), and to the Corinthian Yacht Club in Tiburon, for providing locations and Internet connectivity for our receivers.

      Ship Traffic on the Bay

      During the year that we've been collecting data, we've logged more than 1,700 different ships in the bay. Many, but not all, of the ships provide an identifying type code; using this code, we count the following number of different ships (many of which appeared multiple times):

      One of the several 105-foot pilot boats that guide ships into the Bay.

      These numbers don't add up to the total because some ships don't provide their type code, and there are some other less-common codes not listed here.

      Note: we've included a random assortment of ship and working boat photos here. Click on any of them to see a larger version. And there's lots more on the site.

      The fishing fleet consists largely of boats less than 60 feet long, so it does not show up here.

      There are type codes for military, law enforcement, and search and rescue (Coast Guard) vessels, and every now and then one shows up, often with a destination of "engine trials". But it is clear that, for the most part, they leave their AIS transponders turned off. It's hard to blame them for not wanting to announce their presence.

      Passenger ferry Sonoma.

      We've also found that errors and omissions in the AIS settings are very common. This data must be programmed into the AIS transponder on the ship by someone working on the ship. There have been about 50 ships with invalid type codes.

      Several of the ferries on the Bay have their length and beam swapped (we detect any case where the beam is greater than the length and swap the numbers). One ship showed its length as 2506 feet. A 600-foot cargo ship showed its type as "sailboat." Most of the errors are blatantly obvious — there are no 2500-foot ships, or ships that are wider than they are long — and often information is simply missing.

      Even the Queen Mary 2 was missing the length and beam data. And the destination and ETA data is often out of date, missing, or inaccurate. We assume the Coast Guard is giving feedback to ship owners and that the number of errors will decrease over time.

      Diverse Destinations

      Many of the destinations reported are unsurprising: Los Angeles and Long Beach are at the top of the list, with a combined total of more than 200 ships listing one or the other as their destination.

      A tanker is escorted through the Golden Gate.

      Various Pacific Northwest destinations, including Vancouver, Seattle, and Tacoma add up to about the same total.

      About 110 ships were headed for the Panama Canal, listing their destination as Balboa, Panama, or simply Panama or Panama Canal.

      Among destinations across the ocean, Tokyo topped the list, with 60 ships headed there, plus another 39 for Yokohama. Korean destinations include Pusan (41), Ulsan (29), and Inchon (6). Chinese destinations were not as common as you might expect, with Ningbo (23) and Shanghai (17) leading the list.

      There were also many destinations that only a few ships were headed for, and which may test your geography knowledge: for example, Covinas (Spain), Fujairah (United Arab Emirates), Kalama (Washington State), Muroran (Japan), Paradip (India), Surabaya (Indonesia), and Tubarao (Brazil).

      And The Winner for the Biggest Ship Is...

      You could be excused for guessing the Queen Mary 2; although her AIS transponder didn't report her length, she is 1,132 feet long.

      One of the largest container ships in the world in terms of capacity, the 1096-foot MSC Texas is a "Post-Panamax" ship (that is, she can't fit through the Panama Canal) with a beam of 140 feet. She carries 8,238 containers.

      However, several Maersk container ships with a length of 1138 feet visted the bay. (Two ships reported greater lengths, but these are mistakes in their AIS programming.)

      There were 27 ships over 1,000 feet long and nearly 300 ships between 900 and 1000 feet.

      Larry Ellison's 190-foot Ronin.

      Among the few pleasure boats with AIS transponders, the M/Y Reverie was the largest, at 229 feet.

      Larry Ellison's 190-foot Ronin came in second, but surely he takes comfort in the fact that this is his "little" yacht — his 454-foot Rising Sun is, unbelievably, more than twice the length of Ronin. (Rising Sun has not been to San Francisco Bay.)

      Moving Forward

      In the coming year, we'll continue to expand our AIS network. We hope to add the Carquinez Strait and South Bay to our coverage (we need locations for additional receivers; let us know if you have one to offer), and to add more features to the map display.

      We're seeking sponsors to help underwrite the cost of operating the system, in return for advertising space on the AIS pages.

      We've also found interest from organizations conducting environmental studies, which want a full year of ship movement data for their studies. We're currently accumulating this data and will provide it at no cost to organizations that need it. (If you have such a need, please let us know.)

      Until Next Month...

      That's all for this month. Please forward this newsletter to anyone who may be interested, and tell your friends about BoatingSF.com!

      Michael Slater

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      708 Gravenstein Hwy. South, PMB 162
      Sebastopol, CA 95472

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