In my experience with this sim, the image of the mast is often times very inconsistent. It will apprear to be a certain height and then the next second its only about 2/3 as tall, which I always assumed was due to the inabilitly of the computer to clearly display the image. With a more substantial object such as a smokestack, this image on the screen remains stable, and it would seem to me that you would get a more reliable result for that reason. I havent tested this idea, but it makes sense, at least in theory. Joe S

That's interesting. I've never seen that effect. I wonder which video cards are affected?

I've noticed the same thing. I assumed this was from the software simulating haze, mirage or any RL visibility factors. It definately makes accurate range estimates a lot harder.

However, as RR points out, the main purpose of long range plotting is to allow you to con the boat and reach a favorable attack position. There is no need to compute a final torpedo firing solution when the target is at long range, at least not ordinarily.

The observation that the mast head "disappears" from sight at distance is very real in this game. I don't know if its just the game resolutions not giving the graphics card enough information to keep them from flickering, or some other graphic "setting" that may help to eliminate this problem (whether its a setting in the game options or through the graphics card itself). Possibly it's a problem specific to the hardware we have sitting on our desks that create this issue but the point is, small pixels of an image do seem to disappear from view at distances they shouldn't. The top of a mast head is a prime example. Without being able to "see" the mast head makes manual targeting with the Stadimeter very unreliable.

Unlike the real world sub commanders, the game only allows for one "height" reference point to be used when calculating range from the Stadimeter. The game chose the top of the mast head. Real world captains had any position on a target to use for the Stadimeter reading as long as a reasonably accurate height dimension could be used in the trigonometry equation. The fact that some of the mast heights in the game are so far off from being reasonably accurate, prompted me to correct them with SCAF. And yes, I took the liberty to use other height reference points besides the mast head for the very reason of the graphic disappearance.

Double R is quite right that the lower the height measurement the greater the error can be if your off a bit with the Stadimeter positioning. At close range the game expects the mast height to be towards the top of the periscopes view (towards the top of the area between the waterline and the top edge of the periscope lens). When a Stadimeter reading is obtained in this area, a misplaced stadimeter position (by just one or two pixel lines) will give an error of only a few (maybe up to 10 or so) yards/meters in range. On the other hand at longer distances from the target, the same height reference point will appear lower within this periscope view area. The error of just one or two pixel lines may create a 15 to 40 yard/meter difference in found range (it will increase even more the closer to the water line you go).

You may ask, How wide is a pixel line anyway? The stock game Telemeter division marks (those are the small marks on the periscope lens) have three pixel lines; one at the top, one in the middle to separate, one at the bottom of a two pixel width line. Add the fact that some mast heights are off by several yards/meters (at a 1500 yard distance a single yard/meter can throw off the calculation by as much as 50 yards/meters; the Hiryu CV should have a mast height of 37.4 meters not 31.0 !!) the stock game puts quite a handicap on manual targeting.

I'm almost ready to release a mod that will give reasonably accurate height and length measurements found in the Recognition Manual. It will allow you the use the periscope Telemeter divisions (the lens marks on the periscope) to calculate "Range" with the aid of a device called an Omnimeter. It will also allow you to obtain "Angle on Bow" of a target by knowing its actual length and measuring the "angled" length of the target counted by the Telemeter divisions. The Omnimeter will use this "difference" to calculate the AoB. An added "Range Dial" will be placed in the game to input a manually found range distance into the TDC for a torpedo firing solution. The American side will be able to use the Position Keeper with the inputted range from the Range Dial to "track" a target just like the Stadimeter or Sonar. These additions coupled with having the stock game optics corrected to what the world view should be sized to (which are well off too), will greatly improve game play when using manual targeting.


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Telemon, as Double R pointed out the actual quoted figures in the "Torpedo Fire Control Manual" are wrong. He's quite right that the errors are very minor, so the instruction is still helpful regardless of inaccuracy.

The corrected figures should read:

Page 5-3. Reading the first paragraph on the page we are told in the figure (Plate II?) the target subtends 5 divisions (of the reticule) in high power and 1¼ divisions in low power. The Manual goes on to state ‘That it is known that at 1000yds 17 ½ yards or 52.356 ft subtends an angle of 1 degree’. It then says that ‘Using this information we can deduce the following formulas(sic):
The formulae given are. R(range) = (19.1h)/n
R(range) = (76.4h)/N

Where R = range in yards.
h = height in feet.
n = number scale divisions in low power.
N = number scale divisions in high power.

From the information given can some one explain to me how the figures 19.1 and 76.4 are derived and how they are related to 17.5 and 52.356?

This is the beauty of the American (and German) periscope. The magnification difference between low power 1.5x and high power 6.0x, are multiples of 4. The formula 19.1 times 4=76.4 are directly related to 1.5x magnification times 4=6x magnification. This multiple is also carried over onto the periscope lens having Telemeter division marks of 8 large divisions marks and 32 smaller division sections. The lens itself was manufactured to have a 32 degree Field of View at low power, an 8 degree FoV at high power (you see how all the pieces fit together!!). It's a known fact that one degree of length is equal to 52.356 feet (or 17.452 yards) at a distance of 1000 yards (we're getting into longitude and latitude, curvature of the earth, degrees, minutes, seconds type stuff now), so using these known factors with the formula makes range finding possible.

Finally the figures referred to in Plate II.
The two worked examples.

(a) For the upper diagram; Range = 76.4 x 120 /5 = 1833.6 yards.

(b) For the lower diagram; Range = 120 x 19.1h/1.25 = 1833.6 yards.

It's hard to figure anything out if you don't get the right formula to start with!!! I wonder if these errors weren't some kind of diversion to keep us simpletons from figuring out this stuff. Or did the guy who proof read this material not know how to use a pencil (or think we wouldn't). :88)

Very interesting. Might someone be able to figure out the cause?





I like the idea of having other reference points, but think the highest point is usually the best. At long range, part of the hull will be below the horizon further reducing the accuracy of any lower pt estimate. Also, its simpler to use mast height for all ships.

Is SCAF incorporated in RFB?





Yes, I've dropped in to monitor your progress. It looks good. :up:


Am I right in assuming that we will still be able to use the stadimeter?

Newcomers, if you don't know CapnScurvy he's spent more time with the stadimeter/periscope system than you've spent playing the game. Matter of fact, probably more than I have spent playing the game. He's by far the authority on this area of Silent Hunter 4 and y'all need to pay attention to his posts. Even including the supermodders, there's nobody who has contributed more to the community and more to the great state of SH4. Scurvy isn't a prima donna and he shoots from the hip. Accurately I might add.:salute:

Capn, I still bet the reason for the "errors" was rounding error coming from the use of slide rules to perform all the calculations. Try it yourself and what you read off the slide rule is what they use for an answer. Real geeks at the time would never perform an arithmetic calculation unless a gun were pointed at their head!

you know i was under the impression that SH4, as opposed to SH3, did in fact allow any reference point to be used, simply by manually setting the stadimeter to whatever "mastheight" you desired. I understand that by clicking the checkbox in the recog manual it always chose the masthead height, but by not checking the box, and instead manually setting the masthead height, you could in fact set it to whatever height you fancied.

is this not your experience?

I think in RFB you can use any point you want, but once you click on the rec manual icon, the stadimeter keeps using the default value. Normally, I like to use the rec manual, since I don't have a ready listing of all the possible reference points and it seems simpler.

there is a diagram and a scale in the recog manual, both of which can be used to determine the height of funnels or top of bridge, or indeed anything

- and this is a stock feature, not rfb

Yes, I know there are the horizontal lines, but isn't the scale different for every ship? Without a known scale it isn't very useful.