Range determination

[Kanelglass]

Hi guys ! My biggest problem when it comes to manual targeting is range determination. Then I'm talking about the stadiometer. I'm pretty good with it when the weather is calm, but as quickly there is a tiny wave, everything goes wrong.:oops:
I already know that I can move the periscope at the same time I'm mixing with the stadiometer, but it's still hard.
Could you give me some advice ?
Thx.

[joegrundman]

it IS one of the hardest things to get to grips with in this game, and if you rely on bearing plots to obtain your solution it becomes an even bigger problem, as errors in range lead to errors in target course and speed.

There are a few things you can do to improve your chances.

Firstly, focus on other methods of getting target course, inlcuding your ability to judge AOB by eye. AOB + poor range estimate is more accurate than two poor range estimates. Also try using the aspect ratio method of getting a good AOB

Secondly, focus on obtaining speed estimates by other methods than bearing plots. Errors in range with this method also lead to large errors in speed estimate. Using the slide rule on a whiz wheel is one way to find target speed, which in short means you try to set up a collision course with the target typically on your beam (ie bearing 90/270 from you). Also you can get speed estimates by observing the time it takes for the ship to cross a fixed point, e.g. your periscope cross hairs. you have to be moving slow, but then you can divide the length of target by time to get speed in m/s. double this to get speed in knots.

Thirdly, if you really want to get a bearing plot, plan on getting a large number of bearings plots in order to even out inaccuracies

Fourthly, focus on closing the gap until the range is close enough that errors become less signiricant, fro example by holding the target on a normal approach course of 90/270 degrees.

Fifthly, if the weather is very rough it can be easier to just count the marks on the periscope and do the maths yourself to find an approximate range (also to be done if you have to use your obs scope for targeting)

With all these methods working together, poor weather is just a little challenge. If you are playing GWX you find the disadvantage of rough weather is much more than compensated for by the bad effect it has on your enemies sonar :up:

[Kanelglass]

Thx for your advice !
I have just started with counting marks in uzo/periscope. It's like you said, it's definitive better to count marks in bad weather.
Now I have much to work on to improve my "aim".:up:
I didn't know about the sonar, that's cool !
For now on, I'm going to love bad weather:arrgh!:
Thx again !

[BarjackU977]

I also use the periscope marks, in rough waters. I "unlock" my target, and put the vertical line with marks on the highest mast, while I try to keep the middle horizontal line on the waterline with the mouse. Once I was where the mast is, I click on the stadimeter icon, and put the stadimeter horizontal line where the mast was.

[frenema]

I just try to get an estimate first then go as close to the target as possible for more precise measure (or wait for the target to come close). At a close range your estimates are pretty close no matter how rough the sea is.

[Puster Bill]

Another alternative is to use stabilized view. It only penalizes you 5%.

[Klaus_Doldinger]

Fourthly, focus on closing the gap until the range is close enough that errors become less signiricant, fro example by holding the target on a normal approach course of 90/270 degrees.

Fifthly, if the weather is very rough it can be easier to just count the marks on the periscope and do the maths yourself to find an approximate range (also to be done if you have to use your obs scope for targeting)

With all these methods working together, poor weather is just a little challenge. If you are playing GWX you find the disadvantage of rough weather is much more than compensated for by the bad effect it has on your enemies sonar :up:

So, if I´ve understood it correctly, the TDC is not useless, simply you must use it at a distance in which the errors will be irrelevant.

I´ll tell my own experience today. For hours I have been shadowing a convoy at 9.000 meters. From radio reports I knew that his estimated speed was 7 knots. At night I closed to the convoy. The calm with light fog had turned to 13mps winds with fog also. I submerged as the convoy made a course change and a escort closed to less than 4.000 meters, I didn´t wanted last minute surprises. I identified several ships and fixed a C3 at 1.500 meters, at 90º AOB more or less. The TDC gave me 7 knots. I fired without doubt and he received the two torpedoes, sinking ten minutes later. Without time to see the effect of the two first fishes I fixed a C2 at more or less 1.700 metres; the first calculation gave me 5 knots; I forgot it as in a convoy all vessels must have same speed and made a second calculation, 1.500 meters (rough seas made it difficult to keep the mouse to calculate height and I was very excited to calculate speed with the periscope crosshairs). The speed was 7 knots, AOB more or less 75º. I fired two torpedoes and BOOOOOOOMMMM!!!! (I only heard it as I ordered dive launching a decoy at the same time).

So... must I think that TDC really can work at close distance??

P.S.: I played GWX 1.03, 100%, no map contacts update.

I´d like to hear about your opinions. Thanks in advance.

[joegrundman]

Sounds to me like you did just fine. Apart from that I don't fully understand your question


So, if I´ve understood it correctly, the TDC is not useless, simply you must use it at a distance in which the errors will be irrelevant.


The TDC is not at all useless. It is an angle solver that will give a 100% accurate firing solution for a virtual target that corresponds to the AOB, range, speed and periscope bearing data that you input into it (I don't believe the game models errors in torpedo performance or the effects of water etc.)

It is your job to make sure that this virtual target corresponds to an actual target. To get an exact match is difficult, but because the actual target has a length, there is room for error. The closer you are to the target, the greater the amount of error you can include in your data while still being sure of hitting the target. If you have very accurate data, then unless the target manoevers, you will be able to hit the target even at maximum range.

Range is the least significant error factor, assuming you are firing on a gyro angle of 000, or close to it. (torpedo tube parallax causes large errors to develop if range is not accurate with large gyro angles). Let us assume that you are firing on a gyro angle of 000 with a torpedo travelling at 30kts against the middle of a 150m target travelling at 7.5kts (to make the maths easier). Assume AOB is accurately determined to be 90.

The torp is travelling at 4x the speed of the target, so for the target to have moved 150 meters from the intended point of impact, the torpedo must have travelled 150x4=600 meters. Therefore, 600m range is the margin of error (or +/-300m) you have in terms of range only to still hit a 150m target.

If you are firing from a range of about 1000m, this margin is an enormous percentage of error (+/-30%), but if you are firing at a long range of 5000 m, it is somewhat less (+/-6%). When using your stadimeter in rough weather, it is these percentages which are important.

You can also see that the margin of error is dependent on the length of the ship, therefore, aim for the big ones! You can also improve your chances when there is reason to doubt your data by using a spread pattern. You can also improve your margin of error by using faster torpedoes.

Obviously errors in speed and AOB, and range inaccuracies when using larger gyro angles greatly increase the error, but again shorter range reduces the chance of a complete miss

[Canovaro]

P.S.: I played GWX 1.03, 100%, no map contacts update.

I´d like to hear about your opinions. Thanks in advance.

My opinion is that you launched a very succesfull attack at 100% realism!
Well done! :up:

[Stealth Hunter]

Estimate the range to target and speed by checking your navigation map. The ship's speed, class, and range are automatically calculated by him, so it's pretty much a walk in the park for the lesser difficulties.

[Tobus]

Tips from my humble person:

- target a ship multiple times, thus getting a better and better solution
- Do the last targeting at range under 1000 meters, range will then not be a problem in targeting (and hitting!)
- when moving the scope, stadimeter or any other viewing-thingy, you can speed up movement while holding down SHIFT, but slow down movement while holding down CTRL. This is a little known fact I think, but especially in targeting (speed and range via stadimeter) this can be very usefull.

Always the basic rule remains: the higher the range to target, the worse your firingsolution will be.

[XLjedi]

Also, try to keep in mind...

The ONLY reason you need to estimate distance in the solution process is to help determine target speed.

If target speed is known (ie. slow = 6-7 knots) the range is irrelevent in the constant bearing formula, just set it to 1000 and don't worry bout it.

...and you can use the SH3 scope just like a whiz-wheel to calculate AoB for you! (That's why solution for single target in a convoy is good for any ship in the convoy.)

If you have a good idea of target TC and speed, there's really no need for additional target observations to arrive at a firing solution.

I seldomly have to use the stadimeter, but something to keep in mind... you can pause the game and still use it. (hint, hint ;))

[Klaus_Doldinger]

Thank you all.

Finally I think that I have the basic ideas for a correct use of the TDC. I said it was useless because at certain angles and ranges it gives you absurd data, like 35 knots for a merchant. I suppose I forgot that if your estimations about range and AOB are not correct (specially at long range), TDC can not only give you a wrong speed, but also a totally incredible one. So I must conclude that TDC is a useful device as long as you are able to use it properly, I mean, if you are able to feed it with more or less correct information, and this is easier at short range and at wider observation angles, where errors are less probable or if any, less important. My problem was that I supposed that TDC should be capable of giving me a valid speed with a reasonable error margin almost at any distance within torpedo range, say 5.000 meters.

In any case, I believe that I was a bit lucky in the attack I have related; although I fired at 90º and 75º AOB and at 000, 1.500 meters is rather a long distance. I believe that before the war Onkel Karl recommended not to fire a torpedo at less than 800m

One more thing: I found very useful the scalimeter to have an idea of the convoy speed at long distance, at 90º or 270º. Once identified a ship, I measured the time it spent crossing the crosshairs, and gave me a result of 8 knots, which is a very approximate estimation for long distance. Also, putting the scalimeter in the bow of a ship and observing that he didn´t cross the crosshairs at 90º, I calculated that the convoy had actually almost my own speed.

I need more practice to measure time and distances with the scalimeter in order to fire a torpedos, and will keep in mind the use of CTRL and SHIFT.

Thank you all for your comments and suggestions, this thread has been one more step in realism for me!:up: :up: :up: :up:

Aaronblood: also I´m learning to use MoBo: excellent and very useful tool for interception. I´ll keep learning his use!:up:

[raduz]

another method of speed determination is the turn count

[joegrundman]

Thank you all.

Finally I think that I have the basic ideas for a correct use of the TDC. I said it was useless because at certain angles and ranges it gives you absurd data, like 35 knots for a merchant. I suppose I forgot that if your estimations about range and AOB are not correct (specially at long range), TDC can not only give you a wrong speed, but also a totally incredible one. So I must conclude that TDC is a useful device as long as you are able to use it properly, I mean, if you are able to feed it with more or less correct information, and this is easier at short range and at wider observation angles, where errors are less probable or if any, less important. My problem was that I supposed that TDC should be capable of giving me a valid speed with a reasonable error margin almost at any distance within torpedo range, say 5.000 meters.


I think there has been a slight misunderstanding in use of terminology. Certainly when i refer to the TDC, i mean the TDC on the attack map (f6) screen.

The automated speed calc tool is part of the notepad. I hardly ever use the notepad for anything other than inputing new ranges. I have usually determined speed and aob in advance. Thanks to the way that the german TDC on the f6 screen works i.e. once correctly set, the AOB remains solved so long as neither you nor the target change course, you can program it as soon as you know the target course and your final approach course. Then you just have to watch for course changes.

The AOB wheel on the notepad is different. That tells your TDC programmer to put that value into the TDC. This can be a problem, because if you use that method to input an AOB into the TDC early and forget to wipe the notepad clean, and then use the notepad, say 4 minutes later to transmit a range measurement you will also resend the old AOB data, which is now out of date, and really screw up your TDC solution. For that reason i only ever use the other notepad features for snapshots at targets of opportunity that i hadn't been able to track properly, or if i've been manoevering frantically and i suddenly see something very large dead ahead. These tend to be within 500m, let alone 1500m!

That speed calc tool is very poor. It is entirely dependent on your AOB and range estimate, and so even quite small errors in range and AOB produce massively inflated errors in speed.

In general i try to use means to determine the 3 pieces of data that are independent of one another. This way errors do not compound so badly.

[Hitman]

Germans used another method for calculating very exact ranges in WW2, partly because their UZOs -unlike what SH3 wrongly shows- had no stadimeter or graded reticles. It is more complicated, but if you dominate using a wiz-wheel like the one I did, it is quite easy: Get target speed and course by steering paralell or calculating differences while overtaking the convoy (Or get it from BDU if the contac report is detailed enough). Now, knowing AOB and speed you just need to observe the change in bearing of the enemy over a period of time. Say you want to use the easy 3.15 minutes rule...you note the bearing to target, start the cronometer and wait 3 minutes and 15 seconds. Then you stop it and note the new bearing to the target. Say it changed 20 degrees to backbord....now all there is left to do is setup your wiz-wheel to show the solution, more or less like this:

A target moving at 8 knots covers 4.11 metres per second. In 3 minutes and 15 seconds it covers 802 metres (So you can convert quickly 8 to 800 with the 3.15 rule). You have now the first side of your triangle. The original AOB was 70º, and the target changed 20 degrees bearing. Those are two angles in the triangle, and because all of them must be together 180º, we know that the other angle is 90º. Align your sine scale in the wiz-wheel so that 70º is opposite the 800 (or 8000) in the range wheel . Now, opposite the 20º you see 2900. That's the range to target when we started our chronometer. Align now the 800 with the 90º angle (Which is also the AOB at the moment to stopping our chronometer) and read opposite the 20º 2700. That's the current range to target :up:

[joegrundman]

Awesome! Yet another way to use the circular slide rule/whiz wheel/SACF/ISWAS thingy.