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  #1  
Old 07-07-2012
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AIS and ShipFinder

I thought I might be able to make use of some kind of AIS device so I was doing a bit of net-based research. I came across a webpage for ShipFinder, which also has a free app, so I downloaded it onto my Ithingy.
One thing I noticed almost immediately was some significant discrepancies in locations of ships. In particular, one of the BC ferries that seemed to be landing at Horseshoe Bay continued for about a mile along Highway 1 (that's the trans-Canada Highway), went right through the marina at Eagle Harbour and then traversed Lighthouse Park.

This mis-information is reflected on both the app AND the website.
According to the website:

"In summary the system works by:

◦Ships broadcast their position via radio signals. (The system is called AIS).
◦This information is picked up by our receivers in the area.
◦The receivers send the data across the internet to our servers.
◦The map you are using gets its data from these servers over the internet."

So, my question is where does the system go wrong? At the AIS source broadcast? At the receivers? At the map (using a different datum?).

I can understand a ship being plotted late but not a ship being plotted on land.

Any ideas?
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Old 07-07-2012
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Re: AIS and ShipFinder

I suspect the problem lies with the overlay map app. Almost like some of the GPS/Plotter charts that have update errors, or those that have not been updated since WW-II.

Gary
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Old 07-07-2012
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Re: AIS and ShipFinder

there's a disclaimer on that app that says something to the effect of its for entertainment only and data may be off by a couple hours. I have found it to be pretty close but wouldn't trust my life to it. The old adage about something being worth what you paid for it seems to be accurate for this app.
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AIS and ShipFinder

On the website map, there is the notation
"Map data 2012". So I am not sure that it is a problem with the map itself. I first thought that it might only be the app that was registering errors but on my computer on the website the same thing occurs. I compared the two just before I posted my first message. Right now, the Queen of Capilano is heading up a main street in the town of Horseshoe Bay. So I come back to one of my original questions. If the AIS data the ship sends out is correct & if the map is up to date, could the difference be in the datum used (I.e. Nad 83 vs ??)....or could the BC ferries be off in their broadcast AIS info?
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