I use ShipfinderHD on an ipad3. I'd like the app to include help/info for:
Regarding the colours please see the key below:
Blue = Passenger
Yellow = Cargo
Black = Tanker
Cyan = High Speed Craft
Orange = Pleasure Craft
Green = Dredger
White = Unspecified/Reserved (Can also mean we are not receiving enough data)
Purple = Pilot
Red = Military Operation
Brown = Dive Vessel
Dinghy = SAR Craft
Helicopter = SAR Aircraft
Stationary vessels can be shown as either standard icons or balloon shapes.
Hope that helps.
We will get it added to the help file!
I'll look into the International Maritime Organization (IMO) classifications for Cargo types too.
I don't yet have a reference guide for these.
Thanks very much for the reply. Since I posted that I have more questions and/or feature requests:
1. Shore-based receivers send the broadcasted data from the ships through the internet to Shipfinder's server. Your app gets this data. There is no one official global standard "AIS" server per se. AIS was never really intended for this type of application. Sure, it works fine, but it was intended for ship-to-ship or ship-to-shore(in the form of a Vessel Traffic Control/Service). It was originally envisioned for primarily ship-to-ship, with a roughly 20 nautical mile range just like VHF radio. That original intent is still its primary use as an early warning and collision avoidance system. Simply knowing another vessel's name when calling him for meeting/passing arrangements is revolutionary.
AIS data is the ship's broadcast of where it thinks it is based on that ship's own GPS position. If the ship has a lousy GPS, then the position may be off by a few hundred feet. Typically, this is not the case. Most ships I have handled are accurate to 6 feet or less. It's pretty common to see a ship with D-GPS give a position accurate to less than 2 feet. The ship calculates its position and sends that position value out for anyone listening. AIS is perfectly precise in that it sends exactly that ship's position.
The catch is that moving vessels typically transmit their course/speed/position data once every 2 seconds. Everything else is much less frequent. The other ship data is sent less often. Vessels that are stopped/moored/anchored transmit even less often and at only half power.
I recommend you read the wikipedia article on AIS.
2. The info on the ship data popup is made of 2 parts: Ship static data, such as vessel type, dimensions, and GPS antenna position relative to the ship's centerline at the bow(this one's usually hosed on the smaller workboats). Vessel type has many options, including "Tug" and "Towing Vessel." "Tug" is supposed to be for ship docking-assist tugs, while "Towing Vessel" is supposed to be for the boats that push or pull barges and such. It's common to see these mislabeled. "Passenger" can mean a 75-foot ferry or a 982-foot cruise ship. I also see the tugs that push tank barges for fueling up ships labeled as "Tanker," which is way wrong.
IMO requires the data to be correct, but there is no uniform enforcement in the global shipping industry. If you get into a collision, and your antenna offset from bow was set to 0, while it was in reality 680 feet as is typical on a Panamax, it will not help your case in court. It's the old "There should be a law... oh, wait there are a few, they just arent enforced."
The master of any vessel has the option to turn off his AIS or set it to not transmit(aka receive-only) if he thinks it necessary for the safety of his vessel and crew. I would run transmit only all the time near Somalia or whatever its called now. If you go transmit-only in US waters on a foreign vessel, especially in a river or harbor, you will have the coast guard interrogating you on the radio shortly.
While it is required for 300+ tons, I am seeing it almost universally installed on commercial vessels over the past few years. Fishing vessels are exempt(they have a very good political lobby), but even they are getting the systems(optional for them) installed in drydock now.
I feed data for Vancouver BC to both Shipfinder and MarineTraffic. I find that MarineTraffic's display is 5 minutes or more behind my local display - don't know the reason, but I think I've seen that some 'subscription" sites offer real-time data for subscribers, but delayed data for non-subscribers. I recall that Shipfinder's display was much closer to real time than MarineTraffic, but Shipfinder isn't displaying my data at all at present.
There are two classes of AIS Transponder. Most commercial vessels use Class A, which should fill all the fields on the form. Class B, used by pleasure craft and other voluntarily-equipped vessels omit some data, like destination and ETA.
I think the various AIS display sites are, to some extent, competitors, and therefore don't want to publicise other sites.
I hadn't noticed those before, but by zooming in and out, it seems that they appear when you are zoomed out so that ship icons overlap - the number indicates the number of vessels in that area. If you zoom in, you will see the grey circles dissapear to be replaced by the appropriate number of vessel icons.
fyi - This was captured during Hurricane Issac so lots of ships were in port.