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DougWeb Watchstander's Reference

AIS-Automatic Identification System Map
of the Chesapeake Bay and Vicinity

Click the pin to see the ships.

On-line map created using software from ShipPlotter.com, ShipPlotting.com and Google MapsNow with Baltimore Harbor data from chesbayshipping.com Click the map pin to see the ships.

Welcome to KAF9830 Repeater
Chesapeake Area
GMRS Repeaters.
Families welcome!

Chesapeake Bay Links

Our Goal

Our goal is to show all shipping along the various Maryland coast lines. Consider sending us a direct feed of your data if you buy the ShipPlotter software. Help us expand the view north to Baltimore and south to Virginia Beach, and up our busy rivers.

PopularWireless will also consider placing our own AIS receiving equipment at locations that can provide access to a high-speed full-time Internet connection. We retain ownership of the receiver, antenna, and serial server. All we ask is a place to mount an antenna that we will supply and the Internet connection at your router or switch and and an open port to the serial server. You can arrange sponsorship advertising on PopularWireless.com by allowing us to put our AIS stuff at your your potentially advantageous location. We are looking for high locations with a view of the water at Baltimore, the Patuxent River, and the the Potomac. Data we collect will be used on our AIS page and be forwarded to SiiTech.

Our data is pre-processed by ShipPlotter software and sent directly to the PopularWireless server. Other originators also send directly to our server. No data is ever taken from the COAA - ShipPlotter server - ever. We currently have just one seasonal data contributor and one full-time contributor. We would be happy to send data directly to other ShipPlotter users interested in the Chesapeake Bay.

The PopularWireless copy of ShipPlotter was last connected to the COAA ShipPlotter server on October 22, 2007.

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Ship Scanning and Ship Spotting Links

MarineTraffic.com is keeping track of our AIS statistics. Be sure to look over our map at theior site and look at the cool statistics page. After clicking to the page click on "Refresh Now" to eliminate the coverage map and see the ships.

Update - June 7, 2008. We have data from Baltimore Harbor and Delaware Bay thanks to Bill at ChesBayShipping.com and Alan Henney of Capitol Hill Monitors. Note Alan's feed is seasonal ending in mid-September resuming in the Summer months.

Welcome to the Plum Point, Maryland AIS Receiver. The Google Map link below details the location of ships, tugs, other vessels, bridges, or structures equipped with AIS transmitters and within AIS radio range of Plum Point, Maryland. The AIS radio receiving station is located at Neeld Estate, next to Breezy Point Marina, directly across the Chesapeake Bay from the mouth of the Choptank River. The receiving location can see the Sharp's Island Lighthouse. The receiver antenna is at a height of about 60 feet above sea level and can generally hear ships from just north of the Annapolis Bay Bridge to just south of Solomons Island. During the early morning hours and cooler days in the Summer months the radio receiver may even hear ship signals as far away as Norfolk, Virginia or Cape May, New Jersey. Should you have questions about the method used to display this data you can contact Doug at [email protected]

Do not use this map for navigation. It is provided solely for entertainment purposes and to help GMRS licensees identify ships illegally using our radio frequencies. See articles on the subject at the PopularWireless.com Blog.

On occasion, the data link from the receiving site and the web server may be down. During lightning storms, as an example, the AIS receiver is disconnected from the antenna. When you don't see the ships on the map try again at a later time. When the screen is stuck in "Reading data..." mode try again later. This literally means the radio and the computer are unplugged. In Maryland it is not a question IF you will be struck by lightning but WHEN.

PopularWireless.com now has an AIS Ship Spotting forum where we will try to answer AIS questions and where you can gather with others interested in the ship spotting hobby.

What You See

Each ship is represented on the chart as a map pin. When you reload the page after a few minutes the pins may move up and down the bay. The page reloads itself every five minutes or so. The AIS receiver is reporting movement of the ships. At the north end of the Bay is the Annapolis Anchorage. This is a place where large cargo ships can moor in the Bay waiting for berth at Baltimore. On the south end of the Bay near Lexington park is the Pilot boarding area where pilots come alongside cargo ships to board. Larger ships stay to the eastern side of the Bay in deep water, tugs with barges to the west of deep water. Military ships generally have NO AIS transponders but you will on occasion see law-enforcement vessels and buoy tenders of the U.S. Coast Guard. You will see AIS equipped pleasure craft, tow boats, tug boats, cargo ships, tankers, scientific vessels, and even the tall ships like the Pride of Baltimore.

See a Bigger Map

When you click on the map pin to see the map make your browser go to full screen. Once you have done that press the F11 key on your keyboard. This action will take away the standard browser menu leaving a single menu line across the top of the screen. To get back to the standard view press F11 again.

DSC: Digital Selective Calling

DSC is not AIS and vice versa. Digital Selective Calling or DSC is a data communication mode carried out between ships on channel 70. I monitored DSC with a special computer program also available from ShipPlotter.com for a month and saw one transmission from an international cargo ship. It's expensive to buy so the smaller boats don't use it yet. Using software DSC transmission can be plotted on a map.

Listen to Ships

It is also possible to hear the ships using two-way radios as they transit the Bay. All you need is a conventional scanner radio. Ships are not trunked so an expensive trunking scanner is not a requirement. RadioShack sells a simple $99 hand-held scanner and an inexpensive table-top scanner that can provide satisfactory marine reception. A good outside antenna will always help improve signal strength. Consider the purchase of a tuned marine band antenna and get it as high and in the clear as possible. The marine stores in Deale, Solomons, and Annapolis can help with marine antennas or pick your favorite Internet antenna outlet. I use a J-Pole antenna from Arrow Antennas. The Arrow Antenna J-Pole is designed for wide-band use that includes the frequencies used for AIS. Please note that the antenna coaxial cable or feed line is perhaps the most important part of an antenna system. Use LMR400. cable or better especially on runs over 25 feet. (A more sophisticated scanner with a discriminator tap is required to receive AIS data. Many older scanners available on EBay can be modified to work.)Readers with local scanner questions are welcome to drop by the PopularWireless.com Southern Maryland Scanner Forum to ask questions.

VHF Marine Radio in Southern Maryland
Scanning the Chesapeake Bay

Most large foreign vessels use local VHF channels for navigation purposes. The three most frequently used channels are Channel 9, 13 and 16. PopularWireless.com has an active Marine Radio Forum for those folks that use or have an interest in marine radios. There is also a Southern Maryland Scanning Forumif you have a local question. The complete Coast Guard VHF FM frequency list is located under this link.

  • Channel 9 156.450
  • Channel 16 156.800 The Coast Guard, Coast Guard Auxiliary and some Coast Stations maintain a radio watch on Channel 16. Channel 16 is the hailing and distress frequency. Channel 16 is not for idle chit chat. You MAY NOT conduct a radio check on channel 16. Boaters may conduct radio checks on Channel 9.
  • Channel 13 156.650 Inter-ship Navigation Safety (Bridge-to-bridge). Ships greater than 20m length maintain a listening watch on this channel in US waters. This frequency is used by the larger cargo ships as they transit the Bay.

Listening to VHF marine can provide hours of enjoyment for the boating or scanner enthusiast. Other channels that are fun to listen to include:

  • Channel 10: 156.500
  • Channel 12: 156.600, Annapolis Harbor Control
  • Channel 21 157.05 Coast Guard
  • Channel 22A: 157.100 Coast Guard
  • Channel 23A 157.150 Coast Guard Station Oxford
  • Channel 68 156.425 Harbors
  • Channel 72: 156.625 Harbors
  • Channel 74: 156.725 Harbors
  • Channel 83A: 157.175 Coast Guard, St. Inigoes (St. Mary's County along the Potomac.)

Marine radios cannot be used on land unless the land station is licensed as a marine coast station with the FCC or the station is operated by the Coast Guard or Coast Guard Auxiliary. Marine radios can only be used while a vessel is on the water. When you hear any other use you are listening to radio pirates. It is not uncommon to hear people using these radios car-to-car as they travel to and from their boats. To do so however could earn these folks a serious fine.

Marine channel 70 is for DSC -Digital Selective Calling. No voice is heard on this channel but with the proper marine radio or computer software one can monitor DSC digital traffic. DSC is not very popular yet on the Chesapeake. I monitor DSC and have gone for weeks decoding no DSC traffic. Everything I have seen so far is from the large cargo ships.

Marine channel 68 has been adopted by fishermen as their "fishing channel." During fishing season this channel is alive with conversations. A word to the wise. There are a few people that use language you would not want your children to hear.

Listen to Our Scanner

Bandwidth restrictions required removing this item.

Marine Safety Broadcasts

Listen for marine Safety broadcasts from the Coast Guard and other ships and the local utilities that depend on the bay for commerce. The capable security crew at the Dominion LNG facility can be heard making their security broadcasts on channel 22A warning vessels to remain well clear of the exclusion zone marked by private buoys.

The Coast Guard makes periodic broadcasts announced first on channel 16 that usually move to channel 22A. These broadcasts include regular weather warnings and information, and requests for assistance.

STOP Foreign Shipping Interference

European Maritime Channel Allocations

Foreign Shipping Interference - FSI

In Europe, Africa, and Asia the maritime mobile radio service frequencies cover the entire US General Mobile Radio Service band from 462.5375 to 462.7375 and 467.5375 to 467.7375. Ships have been heard transiting the Bay using EVERY US GMRS channel, While ships normally use these channels in other countries, to do so in the USA is a violation of International Telecommunications Union regulations and treaties signed by the USA. The US National Telecommunications Information Administration is the regulatory authority that specifies what frequencies can be used by visiting ships (under our international treaty agreements) while in the USA. Many visiting ships unfortunately operate with non-standard systems in violation of ITU regulations severely complicating the interference. Some vessels even operate ship-board repeaters with the repeater inputs on 462.575 and the outputs on 467.575. Some have been using 467.575 as an input with 457.525 as an output. These non-standard repeaters wreak havoc on the GMRS band. The General Mobile Radio Service is not the only affected radio service. Business radio systems under FCC R&R Part 90 also suffer FSI. Readers of PopularWireless.com log all instances of FSI at the on-line FSI log, a special forum of the Personal Radio Bulletin Board.

    European UHF Maritime Radio Service Allocation
  • Channel A: 467.525(1)
  • Channel B: 467.550*
  • Channel C: 467.575*
  • Channel D: 457.525(1)
  • Channel E: 457.550
  • Channel F: 457.575(1)
  • Channel G: 467.525(1) 457.525(1) T/R
  • Channel H: 467.550* 457.550(1) T/R
  • Channel J: 467.575* 457.575(1) T/R
    Additional Channels used on UK Ships
  • 457.5375
  • 457.5625
  • 467.5375 (Unoccupied GMRS band-edge channel in US)
  • 467.5625 (FRS channel 8 in US)

(*) Channels allocated to United States General Mobile Radio Service and are not permitted for use by foreign vessels in U.S. waters. (1)These frequencies are allocated for use by foreign vessels in US waters. See the FSI section of the PopularWireless.com Blog for more information. (T/R) Repeater station, First frequency transmitting, second receiving. Updated by the FCC in 2005.

NTIA Footnotes: 669--In the maritime mobile service, the frequencies 457.525 MHz, 457.550 MHz, 457.575 MHz, 467.525 MHz, 467.550 MHz and 467.575 MHz may be used by on-board communication stations. The use of these frequencies in territorial waters may be subject to the national regulations of the administration concerned. The characteristics of the equipment used shall conform to those specified in Appendix 20. 670--In the territorial waters of Canada, the United States and the Philippines, the preferred frequencies for use by on-board communication stations shall be 457.525 MHz, 457.550 MHz, 457.575 MHz and 457.600 MHz paired, respectively, with 467.750 MHz, 467.775 MHz, 467.800 MHz and 467.825 MHz. The characteristics of the equipment used shall conform to those specified in Appendix 20.

As mentioned above, there are other ship's frequency configurations. A ship registered to an African country used every GMRS repeater output channel while in U.S. waters. Ships with registries in Eastern Europe have been heard on 462.675. One ship used 462.575 as a repeater input channel and 467.575 as an output channel with a PL that brought up GMRS repeaters throughout the Eastern United States. A number of FCC Part 90 frequencies are also in use by ships that do not hold US FCC licenses: 457.025 to mention one. Go here Cruise Ship Frequencies to find frequencies in use by cruise ships in your ports. One ship is even using the US Family Radio Service channels for their housekeeping staffs. Please share anything you discover that's new with this website and with PopularWireless. Abuse is not limited to foreign visitors. US flagged vessels are also found using the same GMRS input channels in violation of FCC Rules and ITU regulations.

We Share Data

As of January 23,2008 we now share AIS by direct connection with a another receiver owner in Baltimore, Maryland. PopularWireless data also appears on chesbayshipping.com .

Seasonally we share AIS data with a receiver close to the Delaware Bay.

Tropospheric Ducting and the Rumors

Every once in a while you will see a very large number of ships on the PopularWireless.com AIS Google map extending up to Baltimore, to Delaware Bay, Norfolk, and even well into the Atlantic. Once we even logged ships from New York Harbor.

The PopularWireless AIS receiver is connected to a tuned vertical antenna optimized for AIS frequencies. It is fed by very-low-loss LMR600 coaxial cable. The antenna is about eighty feet above sea level and looks directly over the Chesapeake Bay. It is some eight-hundred feet back from the shore line. The antenna can see Cove Point, Tighlman Island, the Choptank River etc. At some point I plan to change the feed line to heliax so that even weaker signals can be seen on the computer. The antenna system makes all the difference.

We think you should know about a phenomena called tropospheric ducting and why on some days you see many ships on our map and why on other days you only see ships close to the receiving station. Radio signals on the east coast of the United States travel great distances during tropospheric ducting events. The weather actually causes radio signals in the VHF and UHF spectrums to travel farther than normal - sometimes very far. (See Hepburns famous tropo website for predictions!) Tropospheric ducting events give the illusion that many people are contributing data to the website, or that as some extraordinarily impolite Internet list rumors suggest, that we must be using data from other sources! We do not swipe data. Nature gives us the data when the laws of physics work in our favor.

We're awfully tired of the mean-spirited personal email and sleazy mailing-list innuendos from an over-zealous AIS enthusiast that sees a data-sharing conspiracy with every ducting event. The Internet can be so exasperating. Ship watching is an exciting hobby that we want to share with others. Not everyone can afford to set up an AIS receiving station of their own. This page provides a free service to our neighbors using data from our own receiver and others sending data directly to us- period. Enough said.

How did he do that?

Credit where credit is due!
Or I could not have done it without them!

The Automatic Identification System or AIS aboard ships generates a radio signal on 161.975 and 162.025 MHz. Listening on a scanner in AM mode these signals sound like soft popping sounds. In a fraction of a second , data regarding the ship and its movement is conveyed to other ships and land stations for plotting on screens.

The radio signals from the ships are received at Plum Point, Maryland using the SR-161 AIS "Smart Radio" receiver purchased from MilTech Marine. The receiver is very small and runs on only 1.5 watts of power from a twelve-volt DC power supply. The radio is connected to an Arrow Antenna J-Pole via 1/2 inch heliax low-loss coaxial cable to an MCA204M multicoupler and then to the receiver. A serial cable sends the data from the radio to a computer with plenty of computing power.

The software engine and the product that makes it possible to log ships and forward the data to the PopularWireless.com database server is ShipPlotter. ShipPlotter is available for about $30 at ShipPlotter.com.

At the PopularWireless.com web server the mySQL database was created using SQL scripts by Thomas Åkesson. The scripts were included in the ShipPlotter distribution. The database and website is located at the web service provider Network Solutions.

The server-side Google Map PHP script used to read and display the data is courtesy of ShipPlotting.com and all maps are of course by Google Maps!