Question regarding different range results with different magnifications.

[gmetzo]

Hello everyone.
I am trying to make a video on manual ranging with the graticule method of the periscope. Using the tick marks.

Bstanko6 has a fantastic tutorial for this. In this tutorial Bstanko uses the x6 scope of the mag ui and presents us with the following formula.

Mast height divided by tick marks = x number
x number multiplied by 0.22 ( a number specific to the x6 periscope ) = r number
r number multiplied by 1000 = range in meters.

If we take this and apply it to the naval academy torpedo mission , the closest target which is a tramp steamer is estimated , if you enable the automatic solution , at ~800-850 meters.

If we identify the tramp steamer , it has a mast height of 24.1 which we can round down to 24 for easier math.

Using the 6 times scope like bstanko6 does , we see that the heighest mast reaches about 6 marks in our perscope. Therefore , we take the rounded down mast height value of 24 and divide it by a rounded up tick mark value of 6.

24 divided by 6 = 4

We take this result and multiply it with the 0.22 number which according to bstanko6 is a number that is only relevant to the x6 periscope.

so 4 multiplied by 0.22 = 0.88

We then multiply the result with 1000 to find the range in meters.

so 0.88 multiplied by 1000 gives us a range of 880 meters which falls withing the acceptable range of error given that we rounded things up for easier math.

I could let it go here , but what if we use different UI mods or different magnifications? What happens when for example , we use Mag UI in x1.5 or when we use ARB in x6 that has different markings than Mag UI or vanilla?

Do you see where I am going?

Now knowing the range to the target , you can just experiment with numbers all day long and find the right " magic numbers ". Because if for example you know for a fact through cheating , that the target is located 800 meters away from you , you can then find the right numbers to use in your calculations to always result to 800 meters.

Bstanko6 himself has admitted to that and there is no shame in it.

However I am trying to get deeper into the rabbit hole and make sense of all these magic numbers.

I came across this http://www.tvre.org/en/acquiring-torpedo-firing-data as well as Hitman's periscope mods documentations.

Both instances present completely different information and in fact omit vital details , resulting in severe confusion for the reader.

Let's examine hitman's case for example. And I quote :

Target height x 1000 / Scale marks = Distance in meters
For example, a 25 metres mast destroyer on the “10” mark would be at
25x1000 / 10 = 250 metres at 1,5x zoom and 4 times that at 6x zoom (1000
metres)

Let's take his example and apply it to the exact same naval academy scenario.

so target hight x 1000 means 24 x1000 = 24.000 .

We then need to divide this number with the marks. So for the 6x periscope , we will use again the 6 tick marks and so

24.000 / 6 = 4.000 Needless to say this is wrong.

Let's examine the tvre example I linked above. And I quote :

The distance to the target based on the target height was calculated as follows:
distance (kilometers) = target height (meters) / angular target height (angular mils)
For example, the distance to the sinking merchant ship visible in the photo is (assuming mast height equal to 20 meters):
20/120 = about 170 meters when periscope magnification is 1,5x and about 650 meters when magnification is 6x.

First and foremost , this is so badly written I don't know where to even begin. The author says that the method of determining the range is mast height / tick marks. And gives an example with a mast value of 20.

He decides to arbitrarily divide 20 with 120 ( where does he take 120 from? ) . This results in 0.166666666666666666 ( never ends ).

Without explanation he then claims this results in 170 meters. I am going to assume that what he did is round down to 0.166 then multiply by 1000 which results in rounded value of 170 meters and that is for the x1.5 periscope. He then declares again with zero explanation that the distance for the x6 is gonna be 650 instead.

And now I am asking this. If for a moment we forget how badly written this whole thing is , how is it possible for different magnification levels to give off different ranges? So you mean to tell me that the target teleports from 170 meters to 650 meters ?

I am breaking my head against the wall guys. I know bstanko6's method works fine. I know I can just leave it at that , work out the magic numbers that make the math give me what I want and pretend there is nothing else to it. However , even if I didn't want to make a video explaining all this , even if it was just for personal ease of mind , I could never rest easy knowing that I never figured out this mathematical problem. It's driving me nuts I tell you!


If the actual people who are knowledgeable in this stuff such as bstanko6 or hitman could possibly reply to this I would be eternally grateful.

I've got some time preassure going on , so the sooner we can figure this out the better. I am awaiting your replies with great anticipation.

[derstosstrupp]

The scope graticle you see Maciek showing on TVre.org is the historically-correct one for wartime scopes (both the C/2 attack scope and the NLSR “obs” scope). Its vertical scale is in 10/16°. The horizontal scale is in whole degrees (valid for 1.5x only). The horizontal scale is useful for quickly eyeballing a spread.

For ranging, you take the mast height / tan (# of marks * 10/16). Multiply answer by 4 if using 6x. TVre.org shows the range tables from MDv 416T which took the work out of it.

I can’t speak to the GUI bstanko6 is using but the above is at least for historical context. But dividing by his 0.22 is nearly the equivalent of multiplying by 4. If the GUI uses 1.5 and 6, then multiply by 4 as (6/1.5) = 4. Forget the 0.22 then.

I have the manuals for both wartime scope models so any other questions on them, happy to help.

And remember - at low gyro angles, range becomes largely irrelevant to lead angle. So a rough estimate is enough if gyro is within say +/- 30 degrees. Historically it was common to simply estimate range at the shot by how much the target filled the optics horizontally.

[Hooston]

If you treat the angle, range, mast height problem as an arc rather than a triangle you arrive at how the marks are supposed to be used and why 10/16 degrees...

range in m = (mast height in m / target angle in degrees) * (180/pi)

Using the correct historical markings the range in hectometres as entered in the TDC is simply mast height in metres/number of ticks on scope. Unfortunately various mods have messed this up in various ways and it is further complicated by periscope, Uzo and x6 (and in some cases x12) magnification. However whatever your setup the starting point is mast height divided by number of ticks - then multiply by some mod specific scaling factor... Use the convoy attack training mission and have a play with your setup - there's a destroyer nicely positioned ~1km in front of you and it will not attack until you do something unpleasant.

In my case the periscope is marked in degrees at the widest zoom, so at 1.5 zoom

range in metres = 57 x mast height/ticks
but at 6x zoom
range in metres = 230 x mast height/ticks

This puts you back in calculator territory. Most GUI's have some clever tool to do the sums for you. Pedants please note I've rounded the numbers to 2 decimal places!!

As some folks have said you should not need an accurate range, in real life the mast height would not be known accurately and the angle was difficult to measure.

[vanjast]

Two docs here that might be useful.

https://jmp.sh/s/1nZ67o1ZDT84bSn6OEFM

https://jmp.sh/s/cPVplcwIABIF0dPfgoKJ

Free for anyone to use as they see fit... no licenses or charges

[Pisces]

Any of the links posted in this thread are dead 404 links. So I cannot verify the numbers you supposedly take from these "photo's". But yes, the basic equation is actual distance= actual height / observed height, times some correction factor. What that correction factor is, depends on the mod/ or particularly used scale. And technically the zoom factor too.

In the end it doesn't matter when you measure the vertical scale with angles in degrees or radians or whatever. They are slopes that mean a certain rise over a certain distance. For small angles like this, it doesn't matter if you convert a degree or a small fraction of a radian to a slope with the sin or tan scale. They are very much the same. The curves move apart when you get nearer to 45 degrees (or pi/4; halve of square root 2 versus 1) and ultimately towards 90 degrees (halve pi ;1 versus infinity). For small angles it makes no difference in the calculation.

If you want to know the conversion factor used at the end you just work that formula back with known value to find the unkown: the conversion factor:

You know range, you know actual height, you know observed or measured height.

correction factor = actual distance * observed height /actual height

The units for distance or observed height and actual height are not important either, as long as you use the same through out. You measure distance in meters, then keep doing that in meters. If observed height is in scale tickmarks then tickmarks is it. Actual height can be in meters, or the stack number of shoe-boxes. How they relate all end up hidden in the conversion factor. The correction factor is unit-less in essense. Meters divided by meters times some arbitrary sized tickmark interval on screen (pixels if you want). A different zoomlevel just gives you another correction factor to multipy into it.

There is not much to get deeper into the matter really.

[vanjast]

Originally Posted by Pisces

Any of the links posted in this thread are dead 404 links.

They had a 24hr expiry limit..

Anyway.. looking for a anonymous doc upload site like Imgur.
Just not interested in registering/ownership website crap.