the op had another thread about being in a collision at sea underway.
Hi Jon.
I wrote the other thread. I was the buddy boat you mentioned. We were proceeding within the COLREGS, using all of our resources. Had we stopped we would have been just as vulnerable to the skipper of the fishing boat. That we were under way and had steerage I was able to avoid a greater accident. I could have stopped within the 35 feet length of my boat but would have been struck on the starboard side just forward of the mast. As Les the OP on this thread said to me after the event, "I expected to be pulling you from the water and splinters of your boat."
Sail boats with Masts and Radar reflectors 18 feet above the water produce a solid reflection signal to radar receivers and individuals who know how to interpret the reflected signal. Have radar? turn it on and try to identify the targets then confirm them thru visual sightings/binoculars.
In the conditions we faced, and being a solo sailor I would not have proceeded out on the cruise alone. Waiting would have been just fine. Having 2 boats and the equipment to navigate safely our decision to proceed on the cruise was (in my opinion) a reasonable decision. Based on our successful 4.5 hour cruise in challenging conditions across ferry routes with knowledge of where we were and where they were we safely navigated our craft. There is no way of knowing the fishing boat would be out there ignoring all of the rules & regulations we all use to safely cruise the waters. Just like there is no way of knowing the red Honda you see driving towards you will not cross the double yellow line and crash into you. Do you have a plan for this possible event?
So back to the original question... Scanning and understanding signals from radar/AIS is an art just like listening for noises in fog. Fog raises the level of awareness/anxeity. You can not do it for long periods. You will loose focus and that is when you are vulnerable. If you have your head in the cockpit focused only on the screen you are just as vulnerable in fog as when you abandon the electronics and stare out into the grey mist. Work up a scanning procedure and follow it. Check the radar. Have the alarms set for 1 mile or .5 miles. Look at 2 pictures when you scan the radar. Near and far, then switch back to near. Be sure to allow a couple of sweeps to occur at each setting. If you have trails set them to on and moderate tail length. This feature can help when the reflected signal from a target is minimal. You can get a sense of the direction of the minimal target from the tail it leaves. A short tail with gaps may indicate speed of the target. A slow moving target leaves a connected tail. A fast moving target will appear as a series of blips based upon the speed of your antenna rotation.
AIS provides info from transponder sending targets. Commercial traffic is required to have AIS A transponders. This worked well in our trip. We knew well in advance the 8 plus knot Tugs towing barges in the Sound. You need to practice the sequences of your equipment to be able to identify targets that are important and filter out/ignore those that will not cross your path. Can you use DCS calling?
Maybe 5 minutes for all the above. Then you have time to get your head out. Listen to the fog. Boat motors, people talking, horns, sounds picked up by the PA Hailer/Listening feature, or lights coming at you.
5 or so minutes then back to electronics. Sure your going to be busy.
GO out and Practice with all of your equipment. Can you identify a buoy using your radar reflections? Can you see the same buoy during your practice? I know when I flew we would take off and land on a beautiful clear day with a visor over our eyes using only the instruments and radio to guide the plane.
Think out a plan and be prepared to execute it before you leave the dock. It saved my life in the situation I wrote about.