Uh DarkFish, it isn't nice to make fun of others. Especially when the ignorance is yours. Greyrider is on solid ground here.
I shall draw a mental picture and see if you can get up to speed here. With your sonar, you determine a bearing to the target. A simple ping will give you a range. Range plus bearing equals position. Plot the position. Three minutes later, ping again. Range plus bearing equals position number two. Connecting the two positions and extending in the direction of travel gives the target track. With the protractor, clicking ahead of the target position on the track, clicking again on the target position and a third time in the middle of your sub position, you can read the AoB right off the nav map. By inspection with the compass rose on the end of the ruler with help on you can read the target's course. The number of hundred yards between the two positions is the target speed in knots. No superweapons, UFOs, or cute puppies were harmed in this procedure.
Note that the target speed is not necessary to derive the course or AoB. Greyrider is working out another way to determine the speed without plotting two positions 3 minutes apart. I can see this being useful for a visual target where you could use his Mark 1 Eyeball method of measuring AoB. Greyrider is brainstorming here on the message board, and the number one rule of brainstorming is that wacky ideas are encouraged and enthusiastically followed up to see where they lead. We whack people who make fun of ideas over the head with a belaying pin.
