Ranging and fire control problem

[Charos]

I would like to invite others to test and see if they conclude as I have that the Attack periscope as well as the TBT field of view and graticule markers are not correct.

This also affects the TDC as its using the wrong parameters.


The following screenshots are of a stationary Iowa class Battleship broadside With a
S-Class submarine also stationary.

The attack periscope should have a FOV of 8 Deg divided by 32 graticule markers of 0.25 Deg each. (In high magnification 6X setting)

The Iowa is 270M long and has a mast height of 46M.

Now for an 8 Deg FOV to see the Iowa fill the entire screen would require a range of
135M/Tan 4 Deg = 1930M .


Now for a mast height of 46M and a Range of 1406M (This range is from game stadiometer) we see the mast fills 5.5 Graticule markers in the Attack periscope (see attached screen shot)









Each marker SHOULD be 0.25 Deg (IE 8 Deg/32 = 0.25) as per game manual.

Mast /Range = Tan (Theta) in this case Theta = 0.25*5.5 = 1.375 Deg.

Solving for Range = 1916M (Which is very close to the previous 1930M and within error tolerance reading from stadiometer)


Note the Iowa in SH4 fills the 6X attack scope at approx 1680M (see attached screen shot)

Also note that the TDC via the stadiometer provides us a range of 1406M (see attached screen shot)

Something is clearly wrong…Yes?


Now lets dig a little deeper into the problem………………


To cut a long story short the Graticule markers are not 0.25 Deg but approx 0.29 Deg.

135M = Half Iowa Length.
4.64 Deg = Half Attack Periscope FOV.

IE: 135M/4.64 Deg = Range
Range = 1663M (Which is correct in our example).


So that attack periscope markers on 6X and its associated FOV work off 0.29 Deg per graticule marker for its 9.3 Deg of view.

But what happened to our TDC its showing 1406M ????

Well its working off approx 0.34 Deg per marker for Range finding (IE: off the vertical graticule scale) which makes things even more strange.

Hope this all makes sense.

[joea]

Bug!!! ..can it be fixed or modded? My head hurts. Nice work though.

[Joe S]

My math skills are limited to basic multiplication , division, addittion and subtraction. Based on your research, what is the actual magnification of the scope in high and low power? Once we know the magnification, how do we use the recticle to get the range of a target? thanks! Joe S

[Charos]

Originally Posted by Joe S

My math skills are limited to basic multiplication , division, addittion and subtraction. Based on your research, what is the actual magnification of the scope in high and low power? Once we know the magnification, how do we use the recticle to get the range of a target? thanks! Joe S

Joe going by the real life values of the following:


Type II
Magnification high power 6.0X
Magnification low power 1.5X
Maximum elevation of line of
sight (above horizontal) 74.5 degrees
Maximum depression of
line of sight (below horizontal) 10 degrees
True field high power 8 degrees
True field low power 32 degrees
Ranging Device Stadimeter
Telemeter
Scale

Outer diameter reduced section 1.414 in
Optical length 40 ft


Type IV
Magnification high power 6.0X
Magnification low power 1.5X
Maximum elevation of line of
sight (above horizontal) 45 degrees
Maximum depression of
line of sight (below horizontal) 10 degrees
True field high power 8 degrees
True field low power 32 degrees
Ranging Device Radar
Telemeter
Scale

Outer diameter reduced section 3.75 in
Optical length 36 ft


You can see that both the Observation and Attack scopes have 6X and 1.5X
magnification at 8 Deg and 32 Deg Field of view respectively.

You can see that the pattern:

8 Deg = 6X
32 Deg = 1.5X

Therefore 16 Deg = 3X
and 48 Deg = 1.0X

So the attack periscope on high magnification in SH4 provides approx 9.28 Deg FOV
or approx 5.17X magnification.


This whole thing to my mind is the most URGENT Bug in SH4 as it takes the whole TDC measurements out from what they should be.

[Charos]

Im bumping this.

To put this problem in simple terms it means the Games TDC is providing a 17% Ranging error on all firing solutions.

I hope the magnitude of this problem has not been lost in the we need a working chronometer white noise.

In my example above the TDC has clearly provided a range solution of 1,406M while the sub the TDC is sitting in is STATIONARY and approx 1,680M from the target.

[jmr]

Great investigative work here. Hopefully more experienced skippers than myself can give their input on your results. All I can add is that I've been practicing with Kim Ronof's Mark 3B range calculator and my results don't jibe with the auto TDC.

[Charos]

Well they certainly changed the high range periscope FOV BUT they went too far the other way this time.

The Iowa is 270M long and has a mast height of 46M.
Real 8 Deg FOV scope to see the Iowa fill the entire screen would require a range of
135M/Tan 4 Deg = 1,930M .

___________________________________

The data from the Patch 1.01 Iowa test:

Note the Iowa in SH4 fills the 6X attack scope at approx 1,680M.(see attached screen shot)

Also note that the TDC via the stadiometer provides us a range of 1,406M.(see attached screen shot)

So that attack periscope markers on 6X and its associated FOV work off 0.29 Deg per graticule marker for its 9.3 Deg of view.
__________________________________

Now the same test in 1.02 provides:

Note the Iowa in SH4 fills the 6X attack scope at approx 2,850M

Also note that the TDC via the stadiometer provides us a range of 2,450M

So that attack periscope markers on 6X and its associated FOV work off 0.17 Deg per graticule marker for its 5.5 Deg of view.
__________________________________


1.01 shows a TDC to real range variance of 19% less and 1.02 shows 16% less.

Still ballparking around the same 17% mark as before now its just blown past in the other direction.

Problem hasnt changed its just been moved in the opposite direction.


EDIT : We now have approx a 9.7X Magnification attack scope. (Should be 6X)

Hopefully everything I typed makes coherent sense as Im still awake at midday after doing night shift.

[Charos]

If anyone is still following

I turned my attention to the Observation Periscope in patch 1.02 .

Low and behold the Observation Scope - seems PERFECT.


The observation scope seems to be exactly 8 Deg FOV in high range and each
graticule marker is spot on at 0.25 Deg per marker.

This coupled with Krupp's excellent work on fixing the mast sizes and models now gives us an accurate fire control system.


On my S-Class the outermost tube diameter and head seems the same on both attack and obsrvation scopes .

The Observation scope I guess may be easier to spot as fas as the AI is concerned though, in any case there is now a working realistic solution useing the observation scope for the time being.

[Jace11]

Great News

[jmr]

So the observation scope has a max zoom of 6x?

Snip from the Fleet Type Submarine Periscope Manual page 137.

"4. The stadimeter scale dials are graduated

for use with the periscope in high power.
When necessary to range on an object more
than 130 feet high, the stadimeter may be
used with the periscope in low power, and
the object set up on the height scale dial at
one-fourth its actual height. The range
reading is then correct."

The actual Stadimeter was installed with a "Course Angle Finder" as well as the Range Finder. What you did was, similar to the range finder, to adjust an image in length so it would fit with the actual image. Thus you could read out a Course Angle at the Stadimeter on the periscope....neet WE WANT THAT UBI

[Charos]

Originally Posted by jmr

So the observation scope has a max zoom of 6x?

From what I have read and understand both the Attack and Observation periscope are both 1.5X and 6X magnification in low and high range respectively.

You may ask then why both scopes?

Well the following comes to mind:

#1 Obs scope has less optics- In reality I dont think it is kitted with a stadimeter.

#2 Its a backup should the optics go in the main scope due to pressure via normal operations or depth charges.

#3 It has larger ojective lense and optics - just like a telescope it will gather more light and resolve smaller/fainter objects better IE: Stars and planes.

#4 It has a greater vertical range of movement.

#5 Downside is that for all its advantages the Obsevation scope is easier to spot when in use than the attack periscope.