Use of AIS

For those who do not use AIS, but may be interested, here is a short primer on it's use. Can't encourage a purchase enough, especially if you sail in busy ship areas

In this instance, I installed an inexpensive receiver with an antenna splitter. It is attached to my laptop via USB. I use an independent blue tooth GPS unit for positioning with the laptop.

Later I added a splitter and connected it to my C80 Plotter as well, so I now have AIS on both. This demo shows the C80 since my laptop Bluetooth receiver is on the fritz again.

Since 2007 AIS transmitters have been approved and one is on my list to buy at some point. Back in 2007 I was planning to transit Newport Harbor, Long Island Sound, the East River, and the Hudson, so I felt I needed the ability to avoid ships, particularly at night! This receiver only was easy to install.

NOTE: Don't forget to click on pictures to enlarge for more detailed viewing.

Dash is the boat shape the ship is the purple wedge shape

On the C80 by placing the cursor over the ship it indicates the speed of the ship, the closest point of approach (CPA), and the time to closest point of approach (TCPA).

By selecting "AIS List" with soft button at the bottom of the screen you get the list of ships currently in range.
Rng = Range in nautical miles (NM)
Brg = Bearing from the bow of Dash, in this instance, the Tregurtha is 37.7 degrees off the port, or left side.

The bearing is critical. If angle is increasing the ship will pass astern, if the angle is decreasing the ship will pass the bow, if bearing does not change you are on a collision course with the ship, and depending on the alarm distance set (normally 1 mile for me), the C80 will sound an alarm the image will enlarge be outlined in red and flash, to warn you of that fact.  See pictures below of what it looks like.

By selecting Paul R. Tregurtha you get the details of the ship, more than you want to know, but much of it useful.
CPA 1.844 NM
TCPA 21m 18s
COG = Course over the ground
SOG = Speed over the ground
I am uncomfortable with less than one NM clearance, you can speed up, slow down, or change course to make changes to the CPA that give more margin when desired.

Here is the Flinterstar information.
CPA 4.046 NM, TCPA 1h 15m 15s

Paul Tregurtha on the bow at 1.8 NM. Note, ship is not on the upbound track. The one the ship should be on is behind Dash. So in fog, don't think ships are necessarily on the correct track. They cut corners to save fuel!

Here is what it looks like from on deck

Flinterstar passing over 4 NM astern. He is closer to the track, but still a long ways off.

It is reassuring to see the actual distance and time to the closest point of approach because when you are on the bow of a ship, even at 3.8 NM it looks scary! This happened later this particular day. See below:  



The Ship Saginaw Approaching Upbound For Marquette

CPA 1.4 NM in 19 minutes!
NOTE: Destination is wrong, he came from the Soo

Here is what it looks like!  I am crossing in front and you can still see his starboard side, not a comfortable feeling.

In the end he passed as the computer said, no closer than 1.4 NM but it made me nervous going in front of him and watching him bear down on me in my little boat!

Here is display after I cleared the shipping lane and he reaches the CPA.

The View At CPA - 1.4 NM

Here is an example of the what it looks like when you receive a warning.  The image is larger, outlined in red, and flashes. 



This is the target at about .5 NM, a tug pushing a barge upbound on Whitefish Bay.

Hope this has been helpful to any potential AIS users on the fence. 

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Below is a little side note of interest regarding my Autotether System.

SIDE NOTE:

This is the Autotether engine shut down unit I installed. Both engines shut down if I fall overboard.

A small remote unit is inserted into my life vest. When the signal is disrupted by me being in the water, or too far away, the engines shut down. I plan to hook this to the autopilot as well, but it remains on the "to do" list.

Essential to this system is a means of getting back aboard when alone, so I installed an additional boarding ladder that can be deployed from the water by simply pulling it down.