more accurate ruler mod?

[Hylky]

Hi!
Im new at this SH series and i just started to play in realistic mode, BUT i really need more accurate ruler so i can count target speed etc. The ruler that i have now only shows like 50-100-150-200m etc, but is there any ruler that shows like 10-20-30-40-50m (mod) and so on...?

i really wanna count the exact speed! :hmmm:

and by the way, is my calculations even correct?:

3min travel range, devided 180 sec, times 2 = KNOT?

Thnx!

EDIT:

In my book this isnt accurate
http://s3.postimg.org/o3wsi668v/hmmm.jpg (http://postimg.org/image/o3wsi668v/)

[Sailor Steve]

Welcome aboard! :sunny:

I can't help with your problem, but someone will be along who can.

[Pisces]

There is no such thing as an exact speed. (My obsessive compulsive precision disorder hates to admit this.) The target is bobbing up and down the waves. So it varies most of the time. Especially if it detected you and is weaving/zigzagging.

If you want better precision in your speed measurements then you should take a longer time between the plots. The average speed is the key. In real life they didn't use tape measures, you know. Of time however there was enough.

3min travel range, devided 180 sec, times 2 = KNOT?Close enough. Accurately it should be multiplied by 1,94. (=3600s/1852m)

But alternately, if you take plots of 3 minutes and 15 seconds then the distance measured in 100m steps is the same as the speed value in knots. 700 meters would become 7 knots.

Atleast, in the real world. Haven't really tested SH5 to see if it somehow has a deformed space-time continuum like somebody recently posted.

[BigWalleye]

First, the three-minute rule, (distance traveled in 3 minutes)/100 = speed in knots, is correct – provided the distance is measured in yards. One nautical mile equals 2025 yards. So a ship which travels 100 yards in 3 minutes travels 2000 yards (60/3*100) in one hour. This is accurate to about 1%, good enough for a firing solution.

But a nautical mile is only 1852 meters. A ship which travels 100 meters in 3 minutes travels 2000 meters in an hour, or about 1.1 knots. So you have to multiply the 3-minute travel distance in meters by 1.1 (or just add 10%) to get the speed in knots. This answer is accurate to within 2%, again good enough for a firing solution.

Now, regarding your request for a more accurate ruler, the ruler (I actually use the compass, but the scale is the same) will measure to the nearest 50 meters. This is within plus or minus 25 meters of the true value. At 10 kt, that is a 2.5% error, not bad, but if that 2% rounding error from above is in the same direction, that could be a 4.5% error in calculated speed. It’s worse for a 5 kt target speed (7%) and better for 15 kt (3%).

Now. let’s consider the effect of a 4.5% speed error. That means the true speed will be 9.5 kt rather than the 10 kt we measured. For a 44 kt torpedo fired with zero gyro angle normal to the target, the correct deflection will be 12 degrees instead of 13 degrees. (13 degrees is the correct deflection for a 10 kt target.) At 1000 meters, a 150 meter long merchant ship will subtend an angle of about 9 degrees. Plenty of room for a 1-degree error there. At 2000 meters, the ship covers 4.5 degrees, still pretty comfy. At 3000 meters, we’re down to 3 degrees, so a 1 degree error could be significant, although 2 fish should ensure one hit.

So, unless you are firing at rather long ranges, the stock measuring tools are more than adequate. And so is a 3-minute speed calculation, provided you remember to add that extra 10% when you are measuring in meters.

Gluck auf!

[Hylky]

Thanks for the info!

[aschar]

If you really want to wait more than 3 minutes to figure out speed, then by all means... but you might already be in position waiting to strike and by the time those 3 minutes are up, a fast moving target may already have passed an ideal spot to fire or worse, be on top of you.

Here's how I do it: You wait 1 minute then measure out the distance, then multiply the distance by 3.25 (this number will represent the distance traveled in the "magical" 3 minutes 15 seconds). And then you divide by 100 and there, you have the target's speed.

So my formula is ("distance in 1 minute" * 3.25) / 100 = speed in knots

[gap]

If in spite of Pisces and BigWalleye's comments you are still looking for more accurate plotting tools, I suggest you these ones: :03:

http://www.subsim.com/radioroom/showpost.php?p=1496255&postcount=1

[BigWalleye]

Certainly, one minute will work as well. Except that multiplying by 3.25 in your head (No calculators now, this is a WW2 sim!) is not likely to be as quick or precise for most people. KISMIF.

Also, please consider this: If we do a 3-minute measurement and the target travels 1000 meters to within plus or minus 25 meters (the best our measuring tools will do) , we know that his speed was between 10.72 and 11.28 kts, or 11.0 kts in game terms. But, if we only do a 1-minute measurement, the same target will travel 350 meters plus or minus 25 meters. That's somewhere between 10.6 and 12.2 kt. Now, was the target's speed 10.5 kts, or was it 12.0 kts? Or were we just a wee bit off, and it was 12.5 kts? That's a 2.6 degree difference in deflection. Still OK at 1000 meters, but more than half the target length at 2000. If you "fire on the wire" at the target center, you could miss clean astern. If you don't have 3 minutes to refine your speed estimate, then you probably muffed the approach, are trying to squeeze off a wing-shot, and baydayoo is gonna rain on you for wasting torpedos.

Gap, the tools in EQuaTool are good-looking and precise. I use them and highly recommend them. But they improve the angular resolution, The length measurement is still given by the automatic plotting routines, and, whether you use the ruler or the compass, the result is only given in 50 meter increments. Improving your angular measurements won't improve the fundamental linear measurement that determines target speed.That's the increase in precision Hylky originally was asking for.

[Pisces]

What BigWalleye said! Shortening the time makes it less accurate, because the crudeness of the distance measurement works against you.

Maybe it's because I learned the ropes in SH3, but I usually lay in wait for the attack in advance for well over 30 minutes. I want to stay well outside of detection range. Especially at the final moment. When you are losing distance because he is closing, and you are moving slow and perpendicular to the track.

So not having time to do (multiple) 3.25 minute plots seems a bit on the hastily side to me. But I suppose, to each his own play style. I guess I am paranoid about detection.