Calculating an ETA - another useful feature from the AIS page.

Once you have picked up a boat by tracking her on the AIS page you can also add your own waypoints - double click on the vessel's current position and then select 'distance to', a yellow box then gives an ETA based on the speed she is currently steaming at on her last fix - thereby providing a pretty accurate idea as to when she might be heading in through the gaps.....
.....as in the Gary M heading through the gaps.