Boatnerd Discussion Forum

Very nice commentary Mr Link.

One slight update. When you hover over a Marine Traffic report it tells you how old it is. For example, at the moment, Amstelborg is in mid-Lake Erie based on a position received 1 hr 23 min ago.

Steve

I don't think any AIS website or application can truly be considered "real time". AIS is radio based, so it is only "real time" when you pick up the radio signals directly. Which you can do with the proper equipment, but radio signals only travel so far. So websites and apps rely on radio receivers (land or satellite based) that pick up the signal, and then transmit it to a computer server, which then stores the data. The software then samples the data and displays it in a tabular or graphic format.

All this data sending, receiving, storing and sampling results in time delays. Some are unintentional and uncontrolled, just like how an e-mail sometimes takes hours to get delivered. Others, like Boatnerd's AIS sample time interval, are intentional to reduce bandwidth needs for constantly sampling many stations spread throughout the Lakes.

Because users are often looking for a particular ship, software developers often show old data if they didn't receive a new position from that ship during the last few rounds of data sampling. This avoids the ship from "falling off the screen" and requiring the user to use a separate search function to search a "historical" database to find the ship's most recently received location. But it also results in confusion when hours or minutes-old data is displayed on the same screen as data received a few seconds ago. SiiTech uses grayed out icons to note vessels that have physically stopped or that don't have a position in the database that is less than an hour old. SiiTech also lets you adjust the screen refresh rate, but the fastest setting allowed for guest users is 60 seconds. I suspect the ShipFinder site has a quicker refresh rate than 60 seconds, and perhaps they let vessels fall off the screen faster. But as cpfan said, looking at the time stamp is the best way to make sure you are looking at a recently reported position. And of course some time stamps are easier to read than others, since some programs do the conversion from Universal Coordinated Time for you while others, like Marine Traffic don't.

Satellite based systems aren't the answer. Yes, they provide better coverage, but the sampling or refresh rate is usually much slower. Marine Traffic says their sample rate is at best once per hour for their lowest cost satellite data.

I tend to look at a variety of AIS sites and then make an educated guess as to which is providing the most up to date data at that point in time for the area I want to monitor. And it will change from day to day and from location to location.

Of course you can go old school, pack up the cooler with snacks and beverages, grab some reading material and head to the nearest shoreline and sit around for the day. I'm not making light of anyone's dependence on AIS, particularly since I use it all the time as well. Just pointing out that only a few short years ago we had nothing better than a few prerecorded tapes from the loading docks and a network of friends to help us try to catch a favorite ship. That often meant hours waiting along the shore hoping your best estimates were somewhat in the ballpark.

Lakewood wrote:You can grab the ais map on duluthharborcam with your mouse and drag the map to different places. I just checked and was able to drag all the way to the east end of Lake Ontario. If you're looking for news, video and/or live webcam coverage of the Welland Canal, then you're right, that site has zero coverage of that area. Hope this helps. :)

A lot of the ships on Lake Erie and Toledo-Port Huron seemed to have numbers (eg 52 or 5) rather than names. Not sure how that works.

Steve

You can grab the ais map on duluthharborcam with your mouse and drag the map to different places. I just checked and was able to drag all the way to the east end of Lake Ontario. If you're looking for news, video and/or live webcam coverage of the Welland Canal, then you're right, that site has zero coverage of that area. Hope this helps. :)

MattJ wrote:I like the duluthharbor.com site. Real time webcams and the ship finder is also real time. Zoom in on a vessel and you can see it moving on screen and it is dead on. Thats what I want to see ships passing Mackinaw bridge. By Port Huron etc as these are not time delayed like soo locks are. The ship finder on duluthharbor sadly only shows from Two Harbors to Duluth.

Presumably you mean http://duluthharborcam.com/. That site uses http://shipfinder.co/ for its AIS map. I just looked at that site again, and it appears to have zero coverage of the Welland Canal, which is why I ignore that site.

Perhaps somebody else can comment on Mackinaw and Port Huron as I don't really watch these locations.

Steve

I like the duluthharbor.com site. Real time webcams and the ship finder is also real time. Zoom in on a vessel and you can see it moving on screen and it is dead on. Thats what I want to see ships passing Mackinaw bridge. By Port Huron etc as these are not time delayed like soo locks are. The ship finder on duluthharbor sadly only shows from Two Harbors to Duluth.

I guess it would be best to know which sites you have tried. I use Marine Traffic and it seems to have good world-wide coverage for free. You can, of course, pay for their satellite service.

Other sites include Siitech, Vessel Finder, Ship Spotting, and probably others. Googling AIS and trying them all is probably your best bet.

BTW, I believe that some webcams (eg SOO Locks) show a delayed picture. When interpreting AIS , you need to check the time stamp. Often with Marine Traffic, the "current" position is minutes or hours old.

Steve

I would like to know what Ship finder for up to date ship locations for Great Lakes but worldwide as well. I tire of looking at free versions showing a ships position and going to a live webcam page only to find out later vessel passed some time ago. I only have a desktop, no I phones etc. I don't have a problem paying for a good service but unsure of who may offer this good service. Any suggestions are appreciated.