FlightAware Discussions

Does anyone monitor AIS (Ship and Vessel Tracking?)

I have a dedicated RPI and a dAISy hat that I track ships and vessels at sea. I’m located about 25 miles from the Atlantic Ocean in South Carolina USA. If I were closer to the ocean, I know I would see more vessels. I currently have a 2meter/70 centimeter Diamond X50 antenna, (that is a problem), up about 14 ft. HAAT, (that is a problem), RG-58X coax, 25 ft., a 6" jumper from a SO239 to a SMA to the dAISy hat.

I see just a few vessels, and I feed them to VesselFinder and AIShub. Does anyone have any advice about better coverage? I do have an option to move the RPI about 12 miles closer to the sea. I’m looking for some “configuration” settings.

Thanks in advance!

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I assume it’s more difficult as they are all “on the ground”, if the tracking works the same way as for flights.

High band VHF is much less LOS than microwaves.

You could always try a filtered preamp: https://store.uputronics.com/index.php?route=product/product&path=59&product_id=93

I’m not aware how the performance of the HAT you are using is compared to using an rtl-sdr dongle.

You need the antenna as high as possible and as close to the sea as possible since AIS is still mostly line of sight and I’ve yet to see a container ship passing overhead.

AIS class A (used on larger vessels) transmits with 12.5W and is usually receivable up to about 50 miles depending on how high the ships (and your) antenna is. Class B used on small craft only uses 2W transmitter power and the antennas are usually much closer to the surface, except on sailing yachts that tend to put them on top of the mast. There is also class B+ which uses 5W, but is still quite new so not as common. Reception range for them is consequently more limited.

Atmospheric ducting can help a lot with range however - I’ve solidly received ships at 150nm away but you can’t count on that all the time.

I haven’t tried any rtl-sdr monitoring on AIS as I don’t live close enough to the sea, but I’ve used it extensively while sailing. Moving the antenna from the pushpit rail (about 1.5m asl) to the top of the mast (12m) made a noticeable difference.


Apparently made by uputronics

Not yet but this is something I’m keen to play with. I’m relatively close to the sea and some major ports. An RTL-SDR dongle supposedly isn’t very good for AIS so the dAISy hat seems to be the way to go.

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Can’t hide money :wink:

Nope. They just sell it.

Made by: https://shop.wegmatt.com/

Another link, with the manufacturer responding: https://www.tindie.com/products/astuder/daisy-hat-ais-receiver-for-raspberry-pi/#specs


The trick is to go on someone else’s boat.


That was precious. Well played by all involved.:rofl:

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This one looks interesting, and the price is reasonable, including the shipping charge to Canada, which is usually much higher:

I’m too far from the St. Lawrence river, but who knows. I don’t think the small vessels on both the Ottawa and Rideau rivers use AIS.


The Montreal guys are in a better position…

Most definitively. I would likely be a lot more familiar with AIS if I lived there.:wink:

I used to decode DSC*, it’s like “AIS” on HF.

*Edited: Thank you @caius for catching it.

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AIS works on 161.975 and 162.025 MHz. How to build a 162.5Mhz antenna (close enough):


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DSC - digital selective calling. Works on marine VHF as well, but it’s much more useful on HF.

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Yep. Like ADS-B with ACARS on VHF and HFDL on HF.

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