UBOAT: Four bearing method to find a target without map contacts

• This method works when the contact remains at a constant speed and constant course.
• You must remain as stationary as possible for the initial bearing measurements.
• You must use a consistent time interval between bearing measurements.

Regarding time intervals – 10 minute intervals is usually too short, but can work in some circumstances if the contact is relatively close by. 15 to 20 should work pretty well. 30 minutes is even better.

If you are playing without using the pause button, you only have the duration of the interval to do your calculations in. So in that case, longer intervals make things easier.

The ships in this game do change course over time, depending on where they are headed. It is possible that you will get unlucky and they will change course in the middle of your calculations.

If you notice this, or something seems wrong, don’t despair, just start over. There’s plenty of time to spare when you’re at sea.

You will need to use the map measurement tools to perform these calculations. Sometimes they can be a little tricky to control properly, but it is manageable. The ruler and the compass are all you need, but creating parallel lines in the game (at least for now) is bothersome. To make it a little easier, I strongly recommend using something like this mod:

https://steamcommunity.com/sharedfiles/filedetails/?id=3270955106
Then you will see the course of every line drawn on the map and you can recreate it in parallel much more easily.

Also, the default map is 3D and if you have curvature enabled, it can skew things slightly. Overall it’s manageable though. Otherwise you can try this mod:

https://steamcommunity.com/sharedfiles/filedetails/?id=2518835584

It can be from a radio message or from hydrophone. If you actually have visual contact this will still work but there are simpler methods available in that scenario.

You may be moving when you first detect the contact. That’s ok. Just stop and take a new bearing when you are still.

Mark the timestamp of the bearing! Mathematically we will call this t = 0 and calculate from there.

Start the stopwatch! We want to take a new bearing after a specific time interval. 20 minutes is generally a reasonable duration. Don’t wait too long in between recording the timestamp & starting the stopwatch.

You can just use the game clock and eyeball it if you don’t want to use the stopwatch, but if you’ve come this far already, why would you take shortcuts?

Using the ruler, mark a line from your sub towards the bearing. Make it long enough that you have some room to work within later. Keep in mind that contacts could be 80km away or more, so make the lines relatively long.

Keep still and wait!

It’s the same process as step one. After each time interval, mark the new bearing lines with the ruler.

Using 20 minutes as the interval (let’s call it x), and looking at the stopwatch:

Bearing one is at t = 0
Bearing two is at t = 20 minutes (0 + x)
Bearing three is at t = 40 minutes (0 + 2x)

You should have something similar to this marked on your map:

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Now we can start the fun stuff.

Select a point (let’s call it R) anywhere on the line of bearing 2. It doesn’t matter where R is at all, just give yourself some room to work and draw in.

Draw a line parallel to bearing 3 that runs through point R and intersects bearing 1.
Draw a line parallel to bearing 1 that runs through point R and intersects bearing 3.

It should look similar to this on the map:

Mark the intersection point on bearing 1 as i1.
Mark the intersection point on bearing 3 as i2.

Using the compass, from point i1 extend its radius until it touches bearing 2. Mark this point as d1.
It should look like this:

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Again using the compass, from point d1 extend the radius until it touches i2.

It should look like this:

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Drawing a line from i1 to i2 line gives you the course that the contact is steering towards.

However this does not tell us the actual speed of the ship, nor its actual location. Just the actual course. The ship could be anywhere parallel to line i1-i2. Remember, we picked point R at random and ended up with this particular result.

It should look like this:

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Measuring the distance of line i1-i2 will give you a “distance travelled” in 40 minutes (t = 2x) for calculation purposes which will be used in the next step, to predict the fourth bearing.

An example would look like this:

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Now that we know the “distance” between i1 and i2, and we know that it is after 40 minutes (time = 2x), we can work out the distance the contact will travel in the next 20 minute time interval.

Using the ruler, we need to extend line i1-i2 to point i3, which is positioned on the same course line and exactly half the distance of i1-i2 away.

You should have something like this:

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The hard work is done and we are nearly finished!

The most important part of this step is remembering that you must move!

You can go in any direction you like, but you need to change course and move somewhere before the next time interval finishes. I recommend moving roughly towards the contact (not away from it) and towards the course it is on. Move somewhere for a while, then stop, then wait to take the fourth bearing after the same time interval has passed.

Mark the intersection of the real fourth bearing on the predicted fourth bearing, call it i4.

You should end up with something like this:

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Congratulations, you now have triangulated the location of the contact and know exactly where it is positioned!

Draw a line parallel to i1-i3 through point i4. This is the actual course line the contact has been on the entire time.

It should look like this:

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On the actual course line, mark where it intersects the first bearing and call it i5.

Measure the distance between i5 to i4. This is how far it has travelled in three intervals of 20 minutes, which is 60 minutes (0 + 3x).

It should look like this:

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Speed = distance / time

Plug in your numbers and you will get the answer. Depending on which units you are using in the game for distance (km, nm) and speed (km/h, knots) you may need to do some conversions. I won’t explain how to do that here (for now).

So, now we know:

• Contact’s speed
• Contact’s course
• Contact’s location (aka its distance from us)

We can now plot our own intercept course based with this information. I also won’t explain how to do that here (again, at least for now).

Happy hunting!