How to calculate speed without notepad if you do not have gods eye enabled on the nav

[CjStaal]

I am at 100% realism. How do I find out their speed without the notepad?

[CjStaal]

I think I know how. Using some trigonometry.

First calculate bearing and range.

Wait about a minute

Calculate bearing and range again.

From there, you know an Angle, and 2 sides of a triangle.

Using a side angle side formula you can calculate distance traveled.

From there, you can divide by the time and you have the speed.

[Best to do this paused, lol.]

I'm hoping there is a better way though.

[Kip336]

You're well on your way to the solution. What you said would actually work, but if we can eliminate the math, it's even less prone to error.

Take your bearing/range estimates exactly every 3 minutes and 15 seconds.

The distance between two points per 100 meters is the speed in knots.

Distance 700 meter? speed is 7 knots

Distance 1200 meter? speed 12. etc.

[Tupolev]

The fixed wire method is good if you know the target's length. Since 1 kt is about .5 m/s, measure the time a ship takes to cross the vertical wire in your scope.

Works best when your own speed is under 2 kts. Also, you can't be turning or pan the scope when this is happening.

My preferred and (in my opinion) most accurate way is to steer a parallel course abeam the target. Match speed so the target stays at the same bearing. Your speed is now the targets speed. May take some fine tuning to get right.

[Topp1967]

Thanks! for the 3 min 15 sec tip - elegantly simple . Going to switch to that tonight, up till now I had been measuring distance over a set time ie how many metres travelled in a minute(s) then converting to kmph then dividing by 1.852 to get speed in knots.

[Zosimus]

I also have a spreadsheet / cheat sheet that I use when stalking a convoy. It tells me how far the convoy will travel in a certain number of minutes. For example, I can look at my sheet and know that a convoy traveling at 8 knots should traverse 15.8 km in 61 minutes.

Obviously, you could say that it will cover 15.55 km in 60 minutes, but I find the .55 awkward to work with. In reality, the convoy will cover 15.81 km in 61 minutes, but that's close enough to 15.8.

I do hourly checks by hydrophone and typically run 15-20 km away from the convoy (depending on the weather). I have noticed that I often get radar contact from the escorts, but they never wander over to check on me. It's early 1943.

[maillemaker]

The 3:15 works if you know the position of the target.

Fixed wire works if you know the length of the target. I don't know if SH3 has a U-JAGD mod or not - it's a special stopwatch that gives you speed based on the length of the target.

I also have a spreadsheet / cheat sheet that I use when stalking a convoy. It tells me how far the convoy will travel in a certain number of minutes.

You can use the nomograph on the right-side of the map to do that, too. Just draw a line through any known two variables to get the third. For example, if you know speed and time, it will tell you distance traveled.

Steve

[Zosimus]

I believe there's a mod that lets you count propeller beats to determine the speed of the ship.

[BigWalleye]

Originally Posted by Zosimus

I believe there's a mod that lets you count propeller beats to determine the speed of the ship.

It's not exactly a mod. It's a set of charts included in Charts Add-On v1.4 and v1.5 by Sublynx (download frfom SubSim). Charts can be installed in SH3 by following Sublynx's directions, or can be printed out and used RW. The sound-speed correlation is already in the game. (At least, this is true for GWX and NYGM.)


An important point that doesn't seem to have been mentioned in this thread is that AI vessels in SH3 always move at an integral number of knots. Just as they always follow courses which are at 5-degree intervals. I believe this was discussed and verified in posts from way back in the early days of SH3's release. AFAIK, these limits are hard-coded. (Obviously, this does not apply when a vessel is changing course and speed, but any measurement taken at such time is useless anyway.) Any measured differences are exclusively the result of observer error. So any method which determines speed to greater precision is a waste of time and effort. And time and effort are critical resources during the approach to attack.

Over and above the fact that AI vessels always travel at integral speeds is the difficulty of setting the TVR target speed dial more accurately than the nearest whole knot. Click-and-dragging to anything better than the nearest whole knot is liable to be fiddly and time-consuming, at a time when you don't have time to spare. So greater precision just isn't practical anyway.

So just get the speed to the nearest knot. 3:15 works fine. A 3-minute run is almost - but NOT QUITE - close enough for most merchants. But you don't have to get it exactly right. 3:13 or 3:20 will usually see you through just as well as 3:15.

BTW, a historically attested (Werner, and others) speed estimation technique is by observing the target's bow wave. SH3 makes this even easier, because the bow-wave graphics for a fine-bowed DD are pretty much the same as for a bluff-bowed tanker. It takes some practice, but at the least it can serve as a lightning-fast check on other methods. And even if you never acquire the confidence to use the bow-wave method for a targeting solution, you will learn to recognize immediately when the target has changed speed. This has several times saved me from wasting a torpedo when the setup changes just prior to firing. Same with AOB.