[namewithhe1d]

I see a couple candidates that passed through on Aug 20

Map of vessels passing through from Aug 18 - Aug 21 https://imgur.com/a/yLedgc6

Left track passed through Aug 18, right two tracks passed through Aug 20.

Vessel Hex Callsign DJ3767 MMSI 211191450 Vessel SY Malika Callsign DK7486 MMSI 211634590

[zelienople]

Hex is a 10m sailboat. Malika is a 12m sailboat.

These boats did not move a 750kg monitoring station, even in a hurricane, which there wasn't.

[namewithhe1d]

I agree.. doubtful, though these are the only vessels passing through the polygon based on AIS

[yorwba]

What tool did you use for that query?

[namewithhe1d]

vesseltracker.com paid service

[ericb]

Out of curiosity, how does it get data? Is it from satellites, or some other method? I've always wondered if small ships at sea are anonymous, or no.

[namewithhe1d]

Essentially, all vessels over a certain tonnage are required to broadcast identification data (AIS) for safety regulation so other vessels can identify them. Many companies now exist that listen in on those public vessel broadcasts and aggregate the date. Messages are sent by the vessels constantly, and terrestrial antenna are installed by companies, or assisted by volunteer hosts to help collect the messages along coastlines. Satellite companies can aggregate as well, but are usually hindered by how often the pass over a certain area (10 minutes of visibility every 90 minutes, depending on the constellation, and the company).

All in, the larger AIS data aggregators collect about 500 million messages a day from around 150,000 vessels through terrestrial and satellite sources. Access to the full feed, with no delay, is sold for up to $500k/year, though typical deal sizes are around $75k/year. Access to online map-based products usually cost around $10k/year.

<== Used to work for one of the large AIS companies

[mirimir]

Are military vessels exempt?

I vaguely remember reading that US warships in recent accidents had stuff ~like this turned off.

[aphextim]

https://www.marinetraffic.com/ has a free version, from their website.

>The system is based on the collection and processing of data transmitted via the AIS (Automatic Identification System). The AIS-Receiving stations that comprise the MarineTraffic network pick-up such data and share it with the MarineTraffic central database.

>All vessels equipped with an AIS transponder emit AIS-data which can be received by any AIS-receiving unit provided it is within range. AIS message packets are encoded in NMEA sentences (64-bit plain text). A sample is shown below:

>!AIVDM,1,1,,B,1INS<8@P001cnWFEdSmh00bT0000,0*38

>The contents of any incoming NMEA sentence can be decoded. This way, information on the following three basic sections can be deducted:

>Dynamic Information, such as the subject vessel’s position, speed, current status, course and rate of turn. Static Information, such as the subject vessel’s name, IMO number, MMSI number, dimensions. Voyage-specific Information, such as the subject vessel's destination, ETA and draught. The central database constantly receives and processes large amounts of AIS-data and stores the most important part of it (together with geographic information on a multitude of ports and areas, vessels' photos and other details). Current positions and/or tracks of vessels are displayed on the MarineTraffic Live Map while Positions History, Vessel Details, Port Conditions and Statistics can be easily found using our dedicated web pages.

From - https://help.marinetraffic.com/hc/en-us/articles/205413667-H...

[Trias11]

How much does it cost to get this data?

They have this "contact us for pricing" form, which means sales dance is in order, which i want to avoid.