Looking for a link for calculating speed.
 

Hey guys,

I am giving up gods-eye mode! I only use it to calculate speed but now that I am getting away from it I was wondering if there is any good tutorial for estimating speed by using the hydrophones?

...or at least a chart that has all the units from GWX 2.1 in it?

Why not try the Speed=Distance x Time calculation using the navigation chart?
Plot your target from point A to point B, account for the time it takes to travel the distance and multiply it by the time it took?

Is it even possible to calculate speed using the hydrophone? :-?

Lanzfeld

Here's a method that works fairly well under various circumstances (rain, fog, darkness, etc.).
http://www.subsim.com/radioroom/showthread.php?t=110619
It might look hard at first but if you play around with it long enough you'll find out that the concept is actually quite easy. :)
I'll look around for the old bink video for this post if you want. Somebody else may have it already uploaded on a file sharing site.

cheers

Here are basic equations for calculating speed:

Distance in kilometers divided by minutes x 32.5 = knots (use the nav map to make estimated points to calculate by)

Length of target ship in meters divided by seconds x 1.943844 = knots (this equation assumes you are at stand still and are observing target through the scope)

Lanzfeld

Link to Ubi forum post and download of video http://forums.ubi.com/eve/forums/a/t...5?r=7821098535 :)


cheers

Thanks guys,

I know all about calculating speed from a plot when you have a know distance. (I am a pilot after all!):doh:

but I was more interested in counting revs from the hydrophone.

I'll try some of these links...

thanks to all!:up:

Lanzfeld

Click on the link under my sig and look for "sound trainer". It's probably what you're looking for but it only works with
stock Silent Hunter III. The prop sounds were changed for GWX.

I'm afraid counting screwbeats with the above mentioned mod is out of the question for GWX 2.1. IIRC it was made for GWX v1.02 or thereabouts. The GWX 2.1 ship sound settings are not compatible.

Your best bet is do bearing analysis (either visual or hydrophonical) to see how it is moving, meanwhile trying to keep up with it. And deduce course and speed along the way. For which plotting, or better 'drawing lines' since you don't have range, on the map is very usefull.
The following link gives crude AOB (when you are stationary) and as such crude course. Which I know is not what you wanted, but that makes the above that much more easy to do to get speed. Turn parallel course. Flank him until he is on your 90 or 270 degrees (it's best to have him just outside his detection range or it's going to take ages). Then mark your own position on the map, and adjust/settle your speed to keep him on that 90/270 degree. After some time your speed does not need changing, so measure your own moved distance (and time taken) during the adjusting speed period and presto!, his speed. Give or take, since the course was crude to begin with. The more time you take for taking the 3 bearings, the better the AOB acuracy.

http://www.subsim.com/radioroom/show...260#post875260


If within visual range, and positive ID, this is your best bet:

Small correction! Not moving ACROSS your periscope viewing direction. Completely at standstill is a bit too restrictive than neccessary. Moving along the viewing direction is no problem. So make sure the scope is at 0 or 180 bearing when you do it moving.

That was actually the preferred method used in real life by the german U-Boat commanders. All data to estimate speed and course as well as zig-zagging pattern was obtained during the overhaul maneuver. The captain would order the U-Boat to change course until following a paralell course to the enemy. He estimated it by watching the tops of masts above the horizon and using the amount of mast visible to judge if the enemy got closer or farther, as well as using separation between masts to judge course changes. Once satisfied with the value collected, an intercept course was plotted and then the U-Boat went ahead full there.

If the U-Boat did not have time or position to do that maneuver, then the fixed wire method of speed measuring was used as quickest and most effective. It is of special good value when doing a dog-leg approach on surface, because you will be always pointing yoru bow at the target.

While at first the overhauling maneuver seems long and boring, it is without doubt the most recomendable method to really know what the target is doing.

Thanks guys! Great community here.

Okay.......LOVING THIS!!!

But doing this manual plotting deal I realize that I need a periscope and UZO that show 1 degree lines and not just 5 degree. I am using OLC2 and GUI Special.

Does anyone know how to get the 1 degree lines in there?

Thanks

What? Doesn't OLC already include the 1 degree indicator??? :-?

Oh yes, the paralleling of target's coarse is a very satisfactory methode. Nevertheless, I insist that the best way is to "KEEP THE BEARING CONSTANT". If you use a BRC wheel, a MUST HAVE for real life lovers and 100% manual targeting. You can obtain the best speed of the target, even for convoys.

This means:

Subspeed*sinusBearingAngle=TargetSpeed*sinusAoB

So:

TargetSpeed=Subspeed*sinusBearingAngle/sinusAoB.

All you have to do is to keep the bearing of the target constant by adjusting your speed and coarse (for targets with AOB < or = 35 DEGREES only). This has the benefit that you don't have to be on serface while the target makes 12kts.

Finally you need an electronic hand calculator to do the mathematical equation, if you don't use a real life BRC wheel which is quite common in this forum.

This works fine for me for submerge attacks untill the end of the war, while keep silent speed 3-4knots.

Nope...mine doesnt.

Maybe the Gui Special has, I can't remember. But his earlier OLC Gui has 5 degree marks in all de optic bearing ribbons. I can't remember if he had a DIY-solution for it though.

It does have a 1 degree scale, but that is a huge circular bitmap for his 'linear' compas ribbon. I suppose it wouldn't look right at the top of the periscopes, if it is at all posible to use it (rotating graphic versus linear dial).

Hitman, if you could help create one. By all means!

Done. Link posted in the new thread opened by Lanzfeld. The bearing indcator comes directly from my NYGM optics mod, so I'm unsure if you will like the result (I have not tested it because I don't have OLC Gui installed, but should work OK) but anyway it's better than nothing.

i do not understand it right, but it sounds interesting. can you clarify this meethod a little bit please?

Constant Bearing Method
 

When two ships are in collision coarse the bearing between them is constant. The Angle on Bow (AOB) is also constant in this case, while the distance is reducing. It is exactly the same thing when you shoot a torpedo. The deflection angle (firing angle) is chosen according to target AOB-Speed and torpedo speed in order to have a constant bearing between them which is the collision coarse of the torpedo.

How to use this in SH3:

When the target is still not visible and you have a hydrophone contact, you try to much your speed and coarse in order to have the target on a constant bearing and distance CLOSING! You will notice this either by the sonarman report or (better) by manually operating the hydrophone. Now in this situation the vectors A and B of the picture below are equal. Of coarse if initially the target has great AOB (more than 30-35), this situation is difficult to happen, as the target travels rapidly ahead. When the target is finally visible and so determining it’s AOB, you have to resolve the following mathematic equation which is obvious from the picture below:

SubSpeed x Sinus(Target Bearing)= TargetSpeed x Sinus(TargetAOB). The only thing that you don’t know is TargetSpeed.
So:

In order to resolve this, you need a calculator (which accepts sinus input). Or you can use the Bearing Rate Computer (BRC) wheel. For this, use these links.
http://www.subsim.com/radioroom/show...+Rate+Computer

http://www.subsim.com/radioroom/show...+Rate+Computer

Notice:

1. After determing the AOB and Speed, estimate immediately the distance you want to shoot and start maneuvering.

2. In bad whether or at night, the target will get too close to be visible and you will not have the time to set a firing coarse. So you need other plotting techniques.

3. In case of a convoy, pick up a ship and try to do the above mentioned things.

4. A benefit is that you don’t have to identify the target.

5. The method is very accurate and simple, if you want to simulate a TDC break down or a Weapon Officer is “KAPUT” and you do everything manually.

HMmm, interesting. If you managed to get into a course that results in a constant bearing situation you allready have enough information to fire, except with a hit uncertainty due to gyro-parallax (for which you need range), and crude aiming (bearing per whole degree, nothing you can do about withoout visual in the periscope).

If you point the periscope to the bearing of the target, and set AOB to 90 (port/starboard in the direction the target is moving), and targetspeed to the length of your vector B (=ownspeed * sin(targetbearing) ) , then the torpedo should be going in the right direction. This gyro-parallax effect is only large at short ranges so might not be a big problem. You only need to gamble on if your torpedos can reach it.

Next time I'm in the game I'm going to try and see if I can 'fire blind' this way.

@Pisces

1. You can use this method also to approach the target, without fear that the target will pass "CONSTANT DISTANCE" and then "MOVING AWAY". When you manage to have constant bearing (target invisible) the target is always "CLOSING" untill it is on top of you.

2. The blind adjustments that you do if the target is invisible are:

If the bearing of the target moves TO your bow, you increase speed and alter your coarse in order to open the bearing. If the bearing MOVES BEHIND you do the oposit.

I remind you that if the target has AOB greater than 30-35degrees this method may be impossible to be implemented.

3. Your solution setting seems logical.