Originally Posted by
_Agrajag_
What's the visible horizon from a periscope, though? Can't be far, can it? Knowing where a ship like this was to within a dozen miles is more than good enough if you're not interested in sinking it, just keeping a tail on it's whereabouts.
Edited:
Just had a poke around on the web. No idea how far out of the water a periscope pokes, but if it was 10ft then the horizon limit is about 4 miles. If it's 20ft the horizon limit is about 6 miles. If it was 30ft the horizon limit is just over 7 miles. Less than I thought. May be periscopes poke a lot higher out of the water though. A 50ft high one could see out to a bit over 9 miles. 50ft seems high to me, could well be wrong though.
Monitoring a vessel can be done at a distance using passive sonar and a series of manoeuvres to get a range and bearing. The sonogram will give more information about the vessel.. The attack periscope (is/was) is used to get a firing solution by acquiring more precise data on the target's course, speed and range, including confirming the identity of the target. It is much smaller than the conventional periscope which has a larger radar cross section but is used at longer distances or where there is no threat. But either way. a trailing submarine is a boat in trail and is outside the scope of my question.