GWX - getting range at PD with 10X scope?

[danmir]

Hey,

I just purchased SHIII about 5 days ago, and installed GWX. I'm new here, so hey all. I've been lurking here the last week or so, figuring out the lingo. Took me a while to "get" AOB. And apologies in advance for noob questions coming!

I, too, was wondering about the scale, so I tried to puzzle it out. I took empirical data at the 10x mag, and charted it in excel. Basically I took measurements with the stadometer at 15, 13, 12, 11, 10, 9, 8, 5 ticks. I'm at work now, I did the charting at home, but the excel sheet linear estimation of the degrees per tick was about 0.156 degrees per tick.

I thought about this, and I have concluded that in GWX at 10x magnification, there are 0.15 degrees per tick. Reason?

- At 1.5x mag, they are 1 degrees per tick. You can verify this yourself, and it makes sense it would work this way.
- At 10x mag the scope tick scale does not stretch or anything.
- Key info: 1.5 / 10 = 0.15
- 1 degree tick gets subdivided by the ratio of the magnification, thus 0.15 degrees per tick
- I think the game engine funny rounding/flooring for the displayed angle moved my measured data slightly off accounting for the 0.156 linear estimation.

What I did find puzzling though was at the even marks, the measured angle would increment right at the marks, where if it was rounding as I would expect, it would be stable at the even marks and sensitive at the odd number marks. Ie @ 8, 8*0.15 = 1.2 degrees. at 7.8*0.15=1.17~=1.2, 8.2*0.15=1.23~=1.2. If it were rounding, i would expect it to be stable at 1.2 degrees at 8 ticks, but its 1.1 just under 8, 1.2 just over. From this I must conclude the displayed degrees aren't rounded; it is floored.

However, even though it displays the floored angle, I think it still uses a more precise angle for range calcs. I have noticed moving it up and down just a bit on the range measurement for which it gives the same angle on the display does give different ranges.

Assuming the top ticks follow the same scale, this leads to some interesting possibilities of measuring the apparent angular length of the ship, knowing range, and the actual length of the ship, you could compute the AOB.

AOB = acos(apparent_length/actual_length)
apparent_length ~= range * sin (angular_length)

AOB ~= acos(range*sin(angular_length)/actual_length)

AOB ~= acos(range*sin(horizontal_ticks*0.15)/actual_length)

[Sailor Steve]

Thanks, danmir, and WELCOME ABOARD!!!

[Puster Bill]

Originally Posted by danmir

Assuming the top ticks follow the same scale, this leads to some interesting possibilities of measuring the apparent angular length of the ship, knowing range, and the actual length of the ship, you could compute the AOB.

AOB = acos(apparent_length/actual_length)
apparent_length ~= range * sin (angular_length)

AOB ~= acos(range*sin(angular_length)/actual_length)

AOB ~= acos(range*sin(horizontal_ticks*0.15)/actual_length)

You could do that, or you could just just use one of these:

http://www.subsim.com/radioroom/show...ighlight=wheel





As I understand it, Hitman (the kind fellow responsible for these wheels) is now working on a template for a wheel to calculate AOB based on length vs. mast height measurements.

[jmr]

Despite being submerged at periscope depth in rough seas the stadimeter is pretty darn useless given the amount of up and down heaving the boat does. Interestingly enough the rocking of the boat at periscope depth in rough seas in SHIV has been toned down greatly making the stadimeter a breaze to use under any sea condition.

Greyrider made several periscope ranging charts which I have saved on my hard drive. If you PM me your email address I can send them to you. However, the charts were made with the 6x max zoom for the periscope and if you're using GWX the max zoom has been upped to 10x so you'll have to use the SHIII Minitweaker to reset it back to 6x.

edit: Oh yeah whiz wheels are cools too!

[MarkShot]

Interesting solution. I never thoughts about setting it back to 6X. A fairly simple and straight forward approach!

[danmir]

Puster Bill,

Maybe this is a good place to ask. I have read 2 threads on these tools, and still I don't really get what function they perform at what convenience! Its a catch22 for me, I have a hard time understanding exactly what they do, and how easily without having the wiz wheel in front of me going along with the thread.


Do you really gain a good bit of time back using one, and do they get rid of all the little 2-boat triangle note pad drawings next to my desk ? If so, I think I may actually build one.

[Hitman]

Assuming the top ticks follow the same scale, this leads to some interesting possibilities of measuring the apparent angular length of the ship, knowing range, and the actual length of the ship, you could compute the AOB.

AOB = acos(apparent_length/actual_length)
apparent_length ~= range * sin (angular_length)

AOB ~= acos(range*sin(angular_length)/actual_length)

AOB ~= acos(range*sin(horizontal_ticks*0.15)/actual_length)

Been there, done that....though much easier

Get my tutorial for SH4 manual targeting, I use the aspect ratio of the ship and the Kriegsmarine used it also in real life, although more in the way you explained (Basically visible length scaled to measured range).

I have ready the templates for a wiz wheel created purposedly for that, here is a sample:

It consists of 3 rings, where the exterior and interior represent the vertical and horizontal marks, and the middle one (Black) the AOB. To determine the AOB of any ship, you just do 2 steps:

1.- Set the middle ring pointer of the black ring (Above the 90º mark) to the standard aspect ratio of that ship (Which you have listed and printed for quicker use). In the example below it is a standard aspect ratio of 3.6

2.- Align the interior and exterior disks according to the number of scope marks the ship covers horizontally (21 in this case) and vertically (5 in this case)

The AOB is then marked in the black ring by the red triangle of the inner wheel (About 42 in this case).

The whole operation takes more or less 8-10 seconds once you are a bit trained on doing it.

[Puster Bill]

Originally Posted by danmir

Puster Bill,

Maybe this is a good place to ask. I have read 2 threads on these tools, and still I don't really get what function they perform at what convenience! Its a catch22 for me, I have a hard time understanding exactly what they do, and how easily without having the wiz wheel in front of me going along with the thread.


Do you really gain a good bit of time back using one, and do they get rid of all the little 2-boat triangle note pad drawings next to my desk ? If so, I think I may actually build one.

Well, the way I use them they don't really save you much time, per se, as you have to take 2 observations of bearing and range. They do make the calculations easier, however, and obviate the need to make an actual drawing.

I highly recommend that you build at least the backside of Hitman's wheel. I've built three different whiz wheels (an old one from SHII days, the American SACF/IS-WAS, and the KM wheel). They work, and work well.

I've also built a couple of circular slide rules, and I often use a pocket sized linear slide rule (a commercial one, a Pickett N200-ES) for targeting. They all work on pretty much the same principle. I use the linear rule when playing on the sly. It's more discreet than the KM wheel.

But yes, it is worth it to build one and play with it.

[danmir]

Wow, thanks hitman and puster. I think I may build one of the simpler ones and see how it goes.

Hitman, thats a cool point, the aspect ratio does make things much easier. I did follow how to use that wheel you had there, and that really is amazing. I don't follow at all how the wheel works though, its like magic, the 42 just pops out. :hmm: I'll have to think on that; but thats part of the fun of all of this.