Stadimeter question
 

When using the Stadimeter, is it necessary to line up the water line of my target with the center line of the periscope? I ask because after viewing the posts here on subsim, and watching many Youtube videos I've gotten confused. Half of them line up with the water line of target, and some do not. It seems like they all appear to get the correct data as they are successful in sinking their target. I've had limited results with Stadimeter, and have been using Sonar to acquire my range.

For example:
Stickied threads above have a few guides.
http://www.subsim.com/radioroom/showthread.php?t=111998 - This guide lines up water line with center of periscope.

http://www.subsim.com/radioroom/show...=108689&page=9 - Video posted here, he doesn't line up the water line. http://www.youtube.com/watch?v=rqPqvi_fJYk

There is numerous cases of this. I just want some clarification :)


Thank you for taking the time to read my post, and for any info/advice.

Silent Hunter 4 v1.5
Real Fleet Boat 2.0

Welcome Aboard
 

Lining up the Periscopes horizontal line with the targets water line is what I understand to be the correct way.

Someone who uses the stadimeter in a certain way may well have devised a system that works for them.

Using the stadimeter frequently I guess you know what works and what doesn't.

Thanks for the welcome, and the replies! After searching through the install directory I found the manual(lol, I honestly have no idea why I didn't check here first). It doesn't exactly say line-up center of periscope to water line of target, but it has an illustration that measures mast height from the water line. I will take this as my answer :) Again thanks for your time!

Welcome to the boat mate. :salute:

In my experience it's not necessary to line up the waterline but I find it helpful to do so, I seem to get better results that way. I try to do everything exactly the same every time.

Opening the torpedo doors, setting torpedo speed and depth and exploder etc well ahead of time, depth at 15'. That will sink most all merchants and even many warships, you can always reset things later if necessary but you'll not forget to do so in the heat of battle. Nothing worse than missing or doing little damage because your fish were set to slow speed or 5 feet or the doors weren't open:/\\!! :/\\!!

A couple of things about using the TDC/PK shooting method.
When using the data entry tools always input the data in this order.

Turn on the PK.
Input Speed first.
Input AoB next and
Last thing is range and bearing.
It will make a difference.

Magic

Welcome Aboard :sunny:

Be advised: I speculate here, because I always used manual targeting BUT never ever ever used the stadimeter to acquire range (there are other methods I prefer).

I recently learned that if you set up the TDC for a so called "Straight Shot" (aka a shot with gyro angle = 000°) having the speed of the target and AOB correctly estimated is enough (aka, range does not matter).

If in the videos you referenced the virtual kaleuns where in fact performing "Straight Shots" the range estimation they took with the stadimeter did not influenced the result a bit, and this could explain why you saw what you saw :)

I always thought that the advantage of the split prism stadimeter was that you didn't need the horizontal line at the target's waterline because as long as you put the waterline of the ghost ship at the top of the mast of the fixed ship that you would subtend the correct angle anyway.

I could be wrong though. :hmmm:

That's my understanding, and I haven't had too many problems doing it this way.

and on the opposite side? Do you take the highest end of a mast or do you take the highest line of the flag of an enemy ship?

greez
McM

I think that can be variable; OTC, for instance, uses different reference points on the ship for different vessels

With Optical Targeting Correction you follow the Recognition Manual's cues as to where to place the Stadimeter's water line image. Each ship can be different. OTC uses the most visible point, then has the reference point marked in red to indicate the spot. The reference point could be a mast top, funnel, super structure, flag mast, carrier flight deck.

That's just the reason OTC has several ships using the top of the flag (where it's attached to the mast) as their reference point. On some ships the flag mast is the tallest point, yet if you look closely at it, some flag masts aren't visible at all......the flag is just waving in the breeze. Where the OTC Recognition Manual has a national flag added to the picture, use the top of the flag's attached side (whether the mast is visible or not) for the height reference point.

All OTC height reference points are fairly accurate. On the contrary, the stock game and other mods have various measurements. Many are off by 30% of what they should be, some by 50% inaccurate.

Getting back to jlry's original question.....No the U.S. Stadimeter does not need to have the waterline lined up with the horizontal line of the periscope to take a reading.

===============

I realize this thread is nearly a year old, the first linked thread (Hitman's Tutorial for 100% Realism Manual Targeting, of 2007) quickly points out the problems the game has with measurements (least that's what Charos points out in the #8 reply):

The problem was the height measurements are inaccurate, plus the Periscope's Graticule Marks (Telemeter Divisions) are inaccurate too! It's little wonder there were issues found with the games manual targeting from the very beginning. That's why OTC was made, to correct these inaccuracy's.

These may be older threads, but the problems with manual targeting are still evident today without OTC.

"yet if you look closely at it, some flag masts aren't visible at all......the flag is just waving in the breeze"

Biggest problem with using mast height at long ranges on a computer, a distant mast can be one pixel wide or zero pixels (invisible), never half a pixel or 3/4 pixel since computers don't do that. What would be a faint thin line in real life is not there on a computer simulation because of the display limitations.

I got interested in OTC after reading this old thread, so I downloaded it and am reading the docs now. My biggest objection to manual targeting has always been "too complicated" since in real life I would have an entire attack team keeping the plot, cranking inputs to the TDC, fiddling with slide rules and the IS/WAS, and of course setting the torpedo depth and opening the outer doors so I wouldn't have to do all that myself.

Reading the PDF on the omnimeter hasn't changed that opinion - it goes through calculating the range to the exact yard, then moving stuff on the slide rule to calculate AOB based on actual target length versus the visual apparent length. Assuming I've identified the target correctly, of course, which is difficult to impossible at long ranges.

The PDF doesn't mention the time factor, "The computer found range in the Position Keeper is 1468 yards to target. That’s reasonably accurate!"

AT THIS MOMENT it's accurate, whoops, the sub is moving and the target is moving, the range is constantly changing, by the time I make the adjustments on the omnimeter and enter the data into the TDC, that 1468 yards range is ancient history.

How do you compensate for the time factor? Or do you just accept that the data is no longer accurate but "close enough for government work"?

I guess by trial, error and experience.

It's the same when you plot the target's true course and speed on the Nav.map with radar.
By the time you move to the A-scope from the PPI screen, read the distance and look up to the bearing dial, go back to the Nav. Map and select the appropriate tool (triangle thingey :know:), about 10sec. will have passed (if you selected the correct tool otherwise 12sec. will have passed)... Where to put the first marker?!?
Put it where the sub is 'now' and draw the line at xxx degree bearing will put you +-150yrds off... Not a big deal IF you do it the same way each time, mess up once and you'll be off by a couple of degrees and that will mess up your plot.