[greyrider]

continuing with the discussion on the 80-10 methed, one could ask, "how do you know your closing target aob is 10 degrees after leading it by 80 degrees".
theres only one way, and thats if the targets bearing remains contant at the 80 degree lead angle.
one thing i am seeing about this angular arrangment is that im begining to think of it as a reference bearing and lead angle, and that you can find the true aob
of the target, even if the target does not remain on a contant bearing.
for instance, take a look at this and see something, what if you set up this angular problem, and no matter how much you adjust the submarines speed,
the target will not remain contant. if that happens, thats a good indication the the aob is not 10 degrees.
this example asumes the target has a starboard aob, this is the same example used in this original post. now if the aob of the target is not 10 degrees,
no matter what, the target is going to advance in bearings,
in my original post, i held the target constant at bearing two eight zero, so it had a 10 aob.
what if it has an 11 degree aob, or more, well you will still certainly close on the target, you will see it when it comes over the horizon, and it will
still be a ninety or near 90 target track, but it wont be good for a accurate speed estimation
but watch this:
using the formula SS x sin LA / sin AOB
where:
ss = sub speed
la = lead angle
aob = target aob
watch what happens when aob other than 10 degrees are present on the target.
ask the sonar man the targets bearing a speed, he will usually tell you a few facts about the target such as bearing, closing moving away, slow med, or fast speed.
medium speed is from 8 knots to 11 knots.in the op, the target held contant at 280, sub speed keeping target constant was 2 knots, so target speed was 11 knots.
if the taqrget cant be held constant, aob is not 10 degrees, it could be more so, at
11 degree aob, plug in formula, do the math,
for an 11 degree aob, sub speed at 2 knots, target speed is 10.3 knots, still within medium speed tolorance
for a 12 degree aob, sub speed 2 knots, target speed is 9.7 still a medium speed.
for a 13 degree aob, sub speed same, target speed is 9.0 knots
14 degree aob everything the same, target speed is 8.3 knots. still within the medium speed tolorance, but as you can see, as the aob increases, the targets speed is decreasing,
so now if you try to plug a 15 degree aob into the formula, your target speed is now 7.8 knots, and now is below medium speed and would be rated as slow speed by the sonar man.
now you know that your target has anywhere from a 10 degree aob to maybe a 15 degree aob, if your sonar man rated the targets speed as medium.
now its just a play with numbers, or maybe a little mapping and plotting to find the targets real speed.
so from this angular settup between target and submarine, you can get either an extremely accurate speed estimation, or one very close.
more to come later.