Quote:
Originally Posted by flag4
'So on the map, you draw your course and the vessel's course and the angle where the lines intersect is the AOB.'
thats cool. i have always struggled with this. im no numbers and angles man - but that one sentence clarifies a lot for me, thanks irish
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Unfortunately
this is wrong (or just a special case, see below). It is not dependent on your course! It is dependent on his course, and where you are in relation to himself! AOB is the angle between the target's bow, and the view from him to you. (in other words from his bow to the center-line of the scope when you are locked on the target)
The above statement from Irish is
ONLY true if you have the periscope pointed to your bow and the target is centered in view. But that is usually to late to consider a torpedo shoot!
If his bow is pointing straight at you in the view then the AOB is 0 degrees. If he is pointing exactly sideways in the view then the AOB is 90 degrees, and he is pointing either his port side or his starboard side. Do note which one it is! If the target is moving exactly away then the AOB is 180 degrees. As said, the angles in between are hard to judge. But it should come with experience. Another angle that is somewhat easy to determine is an AOB of 30 degrees. Then the apparent width of the target (how far away is the bow from the aft end) is halve of the width as if it had a AOB of 90 degrees, or how it would look if you looked side-on.
If you plot his positions on the map then you should be able to plot a line through them, and extending it to his future positions. This becomes the course of the target. If you need to know the AOB then plot the (current) position of the target on that line. Then draw a protractor (angle mouse-tool, "V"-like thingy): The first click needs to be on one of his future positions on the course line. (just somewhere ahead of his current position) The second click should be on the (current) position of the target. The third and last click should be on your own current location. The angle shown in the corner of the protractor tool is the AOB degrees
of that moment. You should note if the angle (and thus you too) is on his left (port) side, or on his right (starboard) side.
Do remember that if the target is far away then the AOB doesn't change much in a minute. But as it gets closer then the AOB changes more quicker. When the AOB is 90 degrees then it is at it's quickest, and afterwards then it slows down to a crawl on the horizon again. So you need to be more quick with all this if he is within a few kilometers.
If you want to enter the AOB in the notepad then the periscope should be pointed at the target when you make up your mind on the number. But do not keep the scope locked as you are trying to enter it on the notepad. Unlock it when you are sure of the right AOB. Then you have all the time to enter it in the TDC or the notepad. Just keep the periscope or uzo pointed as it was until it is set. After that the TDC updates the AOB as you move the scope automatically.
If you make a course change after that then you need to figure out the AOB again from the start.