4 bearing method. Questions to you, captains.

[Von Due]

For those of you who use the 4 bearing method to plot a ship's movement, using the hydrophone, what ingame tools, mods included do you use and how accurate are your plots in terms of
pinpointing the target"s position
determining its course
determining its speed

[bstanko6]

It won't be accurate. Not with hydrophone. You only have general range and speed. It takes a lot of practice.

For range, understand this. You(the player) can enter the hydrophone suite and hear ships up to 34km away. Your sonar man can only hear up to 20km. So if you are under water and your guy yells merchant ship long range at whatever bearing... I would mark a bearing at 20km away. If he is going slow, I place a compass circle at .7 around the bearing and start the clock. Wait 3min 15sec and Mark near the circle edge after hearing his bearing in the suite. And do this 3 more times.

If I hear the ship first, I make a mark at 27km, which is halfway between 20km and 34km. Again general area of the contact.

This gives me a general direction and speed. So I am not searching the ocean for him.

[bstanko6]

Before people jump in, yes it is possible to get very accurate to even fire a torp with out using the periscope. But I think that is too extreme. I would not believe a kaleun would fire an expensive torp without using all tools to his advantage.

So with enough practice you can get accurate, if you want to.

[Von Due]

I do understand that in real life, a good operator would be able to tell with 1 degree uncertainty at best, about what we have in game. What I am curious about though is how accurate do the players get it, without any concern for historical accuracies or inaccuracies but the main question was and still is

What in game tools, mods included do you use and how accurate are you. So

Others, please do chime in with your own experience.

[Aquelarrefox]

Using bearing ring and attract disc you can calculate by 3 lectures a right good direction around ten degrees, enough to flow and or get perpendicular shoot. About speed, I use real navigation and the inaccurate of my displacement get a bad estimation, so bad that listen rpm I have better info in good condition.

Blind shots are a little of Good luck, mute useful with lut for example in a convoy. For single I prefer use periscope. At long range, maybe a black stranger should be a good reference. I think a very long interval like 5 times the first lectures world get a useful value but reading periscope bearing at long range when you can decide the ship length.

That's my opinion

[Von Due]

Greatly appreciated that post, Aquelarrefox!

What is this bearing ring? Have you got a link to that or an image of it?

You mean you get the course right within an error of 10 degrees? That is valuable info to me.

I am terrible at determining speed based on RPM but it is on my radar, to learn it.... one day.

Blind shots are something I never try anymore. I tested them some years back but found I then totally relied on map updates to have any chance greater than none at all. I'd rather not use the map update for a serious career play.


EDIT
In the current test career, I have map updates enabled for reference and checking. Here's the last result.

I plotted my own course and used the stock compass, protractor and ruler as only tools.
Tracked the target by hydrophone. For this test, the hydrophone lines were disregarded completely.

If the hydrophone guy called out 316, I used the protractor to draw an angle to port at 44 degrees, just as it went from 43 to 44 degrees. That is the lower limit of 44 degrees.
Drew another angle to just where it sent from 44 from 45. That was the upper limit.
Anything within that wedge would be reported as 316 degrees.

I repeated this for the next 2 reported bearings to create 3 wedges.

I then halved each wedge with the ruler and used these lines to construct a solutuion to the 4th "bearing" a.k.a the red line. Idea is to have no more than half a degree error.

The red line was constructed 3 times to check the quality of the solution. 2 of the results agreed perfectly and I chose those as my red line, disregarding the 3rd as erroneus.

With map updates enabled, the last bearing for triangulation was drawn directly to the ship icon that was now visible on the map.

The distance between the red line and the ship was 1750 meters.

I assumed the speed and course had been constant all along and traced the path from the current position back across the 3 first bearings.

From where that path crossed the 3rd bearing, I centered the compass and drew a circle out to the ship's current position.

It was about 200 meters short of the 2nd bearing I had drawn.

I marked where the backtracked path crossed the circle and using the protractor, I measured the bearing to that point. It turned out to be pretty much exactly the upper limit of the reported bearing. The report would therefor agree with the protractor and the plot I had done.

Moving the circle I just drew and centered it on the new mark at the upper limit I just found, I checked where the circle would intersect the backtracked path. It was about 100 meters over the 1st bearing. Again, I marked this intersection and measured with the protractor the bearing that would have produced. Again it was in agreement with the reported bearing only this time, it was precicely at the lower limit.

For this particular plot, halving the wedges to minimize possible errors, still gave me a target position more than 1700 meters away from the real position.

Constructed speed now was about 9.3 knots, measured speed was 9.15 knots. Given the inaccuracies in freedrawing the path backwards in time, I say they agree pretty well.

The plot gave me a target speed of 7.6 knots. This is too great a difference to be useful.

The plot gave me a course of 16 degrees NNE.
The backwards construction gave me 15 degrees NNE.
This is well within limits for medium range shots.

I don't see how one can produce more accurate results if one is not using map updates. Blind shots seem to me to be very much about luck and little about plots.

[Aquelarrefox]

look in magui gui. depending of the version where attack disk is.

http://i965.photobucket.com/albums/ae138/sphere94/04-1.png

http://i63.fastpic.ru/big/2014/1115/28/d896ab65d60a3ddcd1caf1d99dc09028.jpg

in last image from left to right:

attack disck- insert 3 to calculate the 4th bearing, aob, sub course and objetive course.

reverse attack disc or ludwaffe disc depending wich mod - can calculate the speed/lenght by logaritmic. Also can reolve sin equation.

aob disc - insert b2-b1 and b3-b1 in bearing method, then arrow indicate the aob angule aproximate at b1. then use attack disck to obtain course. only works with ships getting closing.

i hope this helps a little. better version of this tools is avaible in magui ws with charts addon ws (i have a version with some change in reco graph and minor things)

some times rpm is imposible to me, but i try if values are rasonable ok if not i try another metod. depending on sound sometimes is more easy. not a rule.

[Von Due]

Thank you for the clarifications. Yeah I have those although I haven't really gotten into how to use them all. The slide rule in particular. The AoB tool I have used on occations for quick reference. The B1B2 wheel I think I understand but I haven't used it other than a few tests some time ago. I still don't understand how one can determine AoB at B1 using that wheel. The equation has infinitely many solutions depending on distance to target at B1.

[Aquelarrefox]

Sino.equation in 2 triangle, a side is 2 times the other, replace, then calculate, replace supplementary and I think in some step make a simplification by Taylor or use a raise I don't see now. That's the better tool of game.

[Pisces]

...
aob disc - insert b2-b1 and b3-b1 in bearing method, then arrow indicate the aob angule aproximate at b1. then use attack disck to obtain course. only works with ships getting closing.
...I designed that sliderule myself. Makman94 copied the scales and added some artistic design to make it authentic looking. (for which there is no reason to think it is. I have no indication or proof that this method was available and used by either forces in the WW2 era. I just made it because it works)

http://www.subsim.com/radioroom/showthread.php?t=147719

I don't know why you think that it works only for contacts closing on you. It works also when the contact is moving away and has already passed the point of closest approach. Atleast, the scales I made work. I presume Makman94 kept those intact in his changes.

[Pisces]

Thank you for the clarifications. Yeah I have those although I haven't really gotten into how to use them all. The slide rule in particular. The AoB tool I have used on occations for quick reference. The B1B2 wheel I think I understand but I haven't used it other than a few tests some time ago. I still don't understand how one can determine AoB at B1 using that wheel. The equation has infinitely many solutions depending on distance to target at B1.I used this document (someone linked it here in the forum years ago) to prove it for myself mathematically that one can arrive at a single (AOB/ relative course) solution based on 3 bearings taken at uniform time spacings. (it does not involve range to calculate it, but the expansion/contraction of the bearing differences) It is described on page 4 of the document. (page 259 on the scan) I have since lost my notes and forgot the precise way of working out the mathematical proof. In my memory it took quite some extra steps and paper space with long equations to end up with the co-tangent formula. But it works!

http://ricojansen.nl/downloads/NOE_-_Bearings_Only_TMA.pdf

[Aquelarrefox]

I designed that sliderule myself. Makman94 copied the scales and added some artistic design to make it authentic looking. (for which there is no reason to think it is. I have no indication or prove that this method was available and used by either forces in the WW2 era. I just made it because it works)

http://www.subsim.com/radioroom/showthread.php?t=147719

I don't know why you think that it works only for contacts closing on you. It works also when the contact is moving away and has already passed the point of closest approach. Atleast, the scales I made work. I presume Makman94 kept those intact in his changes.

hi, great works, in deed it should work in any condition becose you are solving triangules. But in pactical if its gettig out at long range, and you use 6 degrees to read, its heavy posibility of get b3-b1 lower than 10 degrees, and the ring couldnt resolve the situation.
If you read b2-b1 higher than 10 degress depending on speed it could go to quick to intercept.

When i hear that its going out, i leave it, and abort listening bearing. If its a convoy, try to follow to wait better state, night or fog to get ahead in superface, to get a better position to read bearing or direct attack, reading aob stimation by marks and disc.

i think they should have some ay to calculate the bearing method, any way if they have they should use the graphic metod same time (some patrol transcription compare speed stimation between "periscope" and "plotting". (in some line of this http://www.uboatarchive.net/KTB66-6.htm).

i get incredible good values using this with bearing from hydrofone operator and the ring, almost for attack postioning. i didnt use it in late war yet, and i dont like blind shots on single ships to be sure about real hidro-ring presition attacking on medium shots. Maybe in tanker maximise posibilites.

stopped you obtain Aob at b1, what you get if you are moving at fix speed?

posible they need use this ring, look at last table in page (interesant info about ll the stuff) http://www.tvre.org/en/acquiring-torpedo-firing-data

[Pisces]

hi, great works, in deed it should work in any condition becose you are solving triangules. But in pactical if its gettig out at long range, and you use 6 degrees to read, its heavy posibility of get b3-b1 lower than 10 degrees, and the ring couldnt resolve the situation.That is true, 6 degrees for b1-b2 against 10 for b1-b3 is the low end of the bearing scales. But you'll see that the same AOB at b1 (152) can be get when you take a longer time period. Doubling the time period makes a new b1-b2 become 10 degrees. Based on AOB 152 this comes against 15 degrees on the b1-b3 scale for the doubled period. This leaves much more room on that scale to adjust if the 3rd bearing contracted more. And you don't need to start over completely. You just dismiss the first b2, and use the old b3 instead of it. Then wait for the new b3 after the doubled period. Al it takes is a little patience.



If you read b2-b1 higher than 10 degress depending on speed it could go to quick to intercept.I don't quite follow what you are saying here. Depending on speed it could be too quick to intercept anyway. I don't understand how b1-b2 higher than 10 degrees makes a difference. Once you figured out where he is going, and the target created some distance by itself, you can surface and chase him with more confidence of meeting him.

Generally speaking, from entering hydrophone range it takes a target the same time to approach you than it takes them to move away and out of range. So if you can track it's motion before it get's to AOB 90, the closest point of approach, then it is just as likely that you could figure out what his course is before it leaves your hydrophone range. After that it is just a matter of flank chasing in the right direction. And you can do that then with more confidence. I wouldn't waste the opportunity.


stopped you obtain Aob at b1, what you get if you are moving at fix speed?When I dive to make a hydrophone check the speed almost comes to a halt. So I don't need to keep moving at a fixed speed. I have no other reason to keep moving and this contact becomes my primary concern in tracking it down. I focus on my prey. But at 1/3rd throttle the bearings will not change much, so you don't need to come to a complete 0 knots stop. But if you must keep a certain speed then it is wise to turn your heading towards (or away from) the target. As your speed component across the bearing is what contributes the most to the drifting of the sound bearing. At least in the short term.

I should not have placed that note at the bottom of my disk about 'angle on relative motion' when moving at speed. It's too confusing. Basically it means that the result given in the window is really the angle between the 1st bearing and the direction of relative movement (of the target). If you translate this line of relative movement onto the tip of your speed vector, then at some place along that line is where the target's speed vector ends. But you do not know how far away that is along it. To figure that out you need to change course or change speed and do another 3-bearing measurement to get a very different relative motion on your new speed vector. Then both lines should cross where the target's speed vector is. Assuming of course it did not change it's course and speed. But this is too complicated in practise. Kuikueg devised a method to get course speed and position while you can be moving and change course. That would be preffered.

http://ricojansen.nl/downloads/the_four_bearings_method_v2,%20Kuikueg.pdf

[Quinte]

@Von Due

First off, I'm quite the rookie when it comes to Silent Hunter, so take this all with a grain of salt.

- I managed to consistently get accurate enough results for a blind shot by using the following setup: MaGUI, bearing lines with no map contact updates, and pausing to make my bearings as precise as possible.
By the way, I can't recommend the MaGUI enough. That thing is awesome)

- In my career, I chose not to pause: Even with the bearing lines on, it gets trickier to get a perfect solution.

- The longer the time interval, the more precise you get, regardless of your plotting accuracy. I usually go with a minimum of 9'45'', or 13', or 16'15'' (those values help me get the speed without having to look at charts or the attack disk), but I find 9'45" seems to be too short of an interval usually. What intervals did you use in your example?

- When I really want to make a blind shot (night and rough conditions, or escorts nearby), I'll usually transition to an adapted version of the Ausdampfverfahren (constant bearing) method, not depending on range estimation. I found this to be the most effective way to get blind hits.

[Von Due]

@Von Due

First off, I'm quite the rookie when it comes to Silent Hunter, so take this all with a grain of salt.

- I managed to consistently get accurate enough results for a blind shot by using the following setup: MaGUI, bearing lines with no map contact updates, and pausing to make my bearings as precise as possible.
By the way, I can't recommend the MaGUI enough. That thing is awesome)

- In my career, I chose not to pause: Even with the bearing lines on, it gets trickier to get a perfect solution.

- The longer the time interval, the more precise you get, regardless of your plotting accuracy. I usually go with a minimum of 9'45'', or 13', or 16'15'' (those values help me get the speed without having to look at charts or the attack disk), but I find 9'45" seems to be too short of an interval usually. What intervals did you use in your example?

- When I really want to make a blind shot (night and rough conditions, or escorts nearby), I'll usually transition to an adapted version of the Ausdampfverfahren (constant bearing) method, not depending on range estimation. I found this to be the most effective way to get blind hits.

Thanks for the informative post!

As for time intervals, this was a 20 minutes time interval plot. They are normally what I prefer for slow to low medium targets. 15 minutes if medium. Just adding, instead of 3 minutes 15 I use 6 minutes 29 seconds then divide the distance by 2. Reason is the actual time interval for a 3 minutes + interval, I calculated would be for 14 point something seconds. Figured 29/2 would be close enough given the inherent inaccuracy in the pixelation and that in really bad weather, a 6.29 plot would better nullify any fluctuation in speed. The 6.29 is rarely used though as I prefer longer time intervals.

Currently I do use MaGui WS with GWX and I wouldn't want to be without either of them.

I agree that pausing gives more accurate plots but I am currently exploring how accurate it can be without the bearing lines and using only plotting tools like ruler, compass, protractor without using pause.

Pisces: Thanks tons for that link!

[Von Due]

Did another test and differently this time in that there was no actual ship within range but what I did was

I drew an arbitrary line representing an imaginary ship's course.

Decided it was traveling at 8 knots and marked on the line where the ship would be at 20 minutes intervals. Did that as close as the pixels and eyesight would allow.

Drew another line representing the sub travelling at 2 knots and marked where the ship would have been at 20 minutes intervals.

Drew lines directly bewteen corresponding marks on both lines to get bearing lines. These would be the accurate bearings.

Measured the angle on these bearings then using the protractor, creating lower limits and upper limits for each measured bearing angle accepting that there is no way to tell, without hydrophone lines, where within the limits the true bearing would be.

Based on these 3 pairs of lower and upper limits, I created 4 red lines.

1st and 2nd red line had the symmetry points based on 2nd bearing, upper limit, 1st bearing lower limit.

3rd and 4th red line had the symmetry point based on 2nd bearing, lower limit, 1st bearing upper limit.

1st and 3rd was further based on the 3rd bearing upper limit.

2nd and 4th was further based on 3rd bearing, lower limit.

The 2nd and 3rd red lines were the ones furthest away from the ship's true position, on the course line I drew first, some 2700m apart.

I chose a 4th position for the sub to do the triangulation, based on what a reasonable speed would allow over 20 minutes.

Result was, without further conciderations that the uncertainty of ship's position in this particular plot, on doing the final 4th bearing, was more than 20 km, approaching 30 km*.

Further considerations: It is valid to anchor each extreme red line with the 2nd anchor of the other extreme red line. This results in 2 even more extreme red lines further apart than 2700m, resulting in even greater uncertainty in pinpointing the ship's position.

However, by using the compass one can find that some combinations of upper and lower limits for each of the 3 bearings result in invalid solutions.

For example, if the ship was at bearing 1's upper limit then it could not possibly have been at the 2nd bearing's upper limit as that would mean it could not have made it to the 3rd bearing in time. In fact, it could not have been at the 1st bearing's upper limit at all.

One can investigate each possibility and eliminate invalid solutions, thus reducing the possible angular span for each bearing but that will take a lot of effort to do just once.

Incidentally, for the 3 true bearings
1st true bearing was very close to halfway between the lower and upper limits.
2nd and 3rd true bearings were both very close to the 1/4 degree mark from the lower limit.

*The 4th bearing for triangulation was the true bearing. I did not create upper and lower limits for this. With upper and lower limits, the uncertainty would be even greater.

[Pisces]

Von Due:

I commend you documenting your efforts, but without a visual representation I find it hard to comment on it or give suggestions. Screenshots would have been nice.

[Von Due]

Von Due:

I commend you documenting your efforts, but without a visual representation I find it hard to comment on it or give suggestions. Screenshots would have been nice.

I didn't take any screenies of this but I could do it again and take screenies if that is necessary. I was thinking a description would at least allow someone else to do the same test with other parameters and get new results, be it worse or better than mine. Again, if necessary I will make another test and make screenies. Might take a while to get it done though.

One more thing I found.

The hydrophone guy sometimes have trouble keeping up with the ship, especially if the change of bearing happens fast, that is less than about 15 seconds apart. On a few occations he would report a bearing of say 44 degrees when the bearing line clearly was at 45 degrees. This complicates things even further. A 1 degree error either way from true bearing would give an unacceptable 3 degree margin for error.

I haven't looked into this possibility but could it be that the accuracy of the hydrophone reports depends on the rank and specialisation of the operator?

[Pisces]

I've noticed the crew report timing is related to the duration of the sound clips (in particular the bearing numbers) they are uttering. That also causes the bearings given to be different from what they are supposed to be at that time. I think it is game lag induced.

I never noticed much difference due to experienced crew. But I never really tested that either.

[Von Due]

I've noticed the crew report timing is related to the duration of the sound clips (in particular the bearing numbers) they are uttering. That also causes the bearings given to be different from what they are supposed to be at that time. I think it is game lag induced.

I never noticed much difference due to experienced crew. But I never really tested that either.

Thank you! The sound clip length makes sense and it made me look into the sounds folder a bit harder. Curiously enough I see speech clips for functions I don't think is in the game, like "Weather report sent". Weather reports were present in SH2 but I never saw any of that in SH3. There are others there as well.

Anyway, back on topic. Looking through the folder now trying to find the set of clips that would make the bearing report.

EDIT
Digging around in the forum I found some posts suggesting that Ubi did indeed leave out a number of planned features in the final product. Wonder if it's perfectly safe to remove these sound clips then or if there are remnants of code that would throw a fit if those files aren't there.

[Sailor Steve]

Digging around in the forum I found some posts suggesting that Ubi did indeed leave out a number of planned features in the final product. Wonder if it's perfectly safe to remove these sound clips then or if there are remnants of code that would throw a fit if those files aren't there.
I've removed sound files with no problems, but the safer way is to use a sound editor such as www.goldwave.com (http://www.goldwave.com) to make the files blank. That way the file is still there, but there's nothing in it.

[Von Due]

I've removed sound files with no problems, but the safer way is to use a sound editor such as www.goldwave.com (http://www.goldwave.com) to make the files blank. That way the file is still there, but there's nothing in it.

Gracias, Sailor Steve. I'm considering the possibility to cut down on these clip lengths but it would take quite a lot of testing to see how it would all work. Would have been nice of Ubi though if they didn't decide the sound guy would constantly remind us that the merchant we are tracking is indeed a merchant and not a warship. Reminds me of the tank sim Steel Panthers*. Get hit by a rifle bullet and for the remaining mission the crew will constantly bellow out We're Hit! Some things are not really necessary. Anyway, I'm rambling.

*Steel Fury, rather. My memory is utter crap sometimes.

[Quinte]

Well, I went ahead and made the experience again, taking screenies this time.

Here is my initial setup: Target is doing about eight knots, on a regular course, sub is doing about two knots on a straight line as well (never mind the fact that this is, from a tactical point of view, stupid: I can't ever hope to intercept my target if it's steaming fast).
http://imgur.com/7VurkOShttp://imgur.com/7VurkOShttp://i.imgur.com/7VurkOS.jpg

First time around, I've drawn my bearings simulating what bearing lines would give me (i.e not quite perfect, but almost).
http://i.imgur.com/anAqJgB.jpg
The Spiess Line is pretty much bang on.
http://i.imgur.com/UZgfRuu.jpg
http://imgur.com/UZgfRuu

I've selected a fourth position from my sub, doing around 7 knots to get there. From ther I draw my last bearing, and obviously, the calculated position of my target, course and its speed are spot on.
http://i.imgur.com/6qpQuOW.jpg
http://imgur.com/8tju2PJ
http://i.imgur.com/8tju2PJ.jpg

Now, I've just changed my last bearing to introduce a 1° error. The result is an error of about 100 meters i the estimated position, the course calculated is still way good enough to take a blind shot.

http://i.imgur.com/UYkNxI7.jpg

http://imgur.com/UYkNxI7http://i.imgur.com/KRkJPnP.jpg
http://imgur.com/KRkJPnP
Okay, so now I've gone and redone the experience tracing my bearings with the stock protractor.
My Spiess Line cuts the actual course with an error of about 500 meters.

http://i.imgur.com/ppbS47O.jpg

But my estimated position after the fourth bearing is way off.
http://i.imgur.com/pCNB9iJ.jpg
http://imgur.com/pCNB9iJ
2400 meters off, actually.
http://imgur.com/9tpGKUThttp://i.imgur.com/9tpGKUT.jpg

The course I calculated, and the speed, are not exploitable (the angle between the actual course and the predicted one is about 19°).
http://imgur.com/0EJnEUE
http://i.imgur.com/0EJnEUE.jpg

So I guess this settles it for me, the four bearings method doesn't seem even remotely useful without using fractions of degrees when taking the bearings.
That said, this was an interesting experiment, and I'll keep playing with it to see how you can maneuver your sub during the setup to minimize the error.

[Von Due]

Thank you tons for bothering doing this! Yeah while the 4 bearing method is, if I may say so, a rather beautiful method and use of geometry, its usefulness without having at least the 10ths of a degree seems to me to be questionable.

EDIT. It should be mentioned that when I plotted this using the exact bearings, the red line was about 5 meters off the ship's exact position and the triangulation resulted in no more than 20 meters error. So, if one had the exact bearings, the 4 bearing method works.

[Sailor Steve]

Would have been nice of Ubi though if they didn't decide the sound guy would constantly remind us that the merchant we are tracking is indeed a merchant and not a warship. Reminds me of the tank sim Steel Panthers.
It's worse than that. They magically report the Auxiliary Cruiser as a warship, when it is in fact a merchant with some guns fitted. Same with the Armed Trawler - it's still a trawler, armed or not. How does a guy listening to the propellers know that? Now that I think of it, the 'Flower'-class Corvette is based on a large trawler design.

Get hit by a rifle bullet and for the remaining mission the crew will constantly bellow out We're Hit! Some things are not really necessary. Anyway, I'm rambling.Please, don't get me started on the crew knowing they've been spotted by a merchant 10 km away and start crouching down and whispering. Same with hydrophones. They know you've been heard at the same time the enemy does.

In my own translation of the Das Boot Sound Mod I tried to change all the Speech files so the only time your crew whisper is when you order Silent Running.

[Von Due]

It certainly looks like the game master side of the game is quite a busybody passing on information neither the player nor the AI should have access to.

[Von Due]

Back on topic:

One thing that might work although it will increase the workload by quite a bit is to note down the time it takes, in seconds, for the bearing to be reported on the neighbouring degree then estimate how close to either extremes true bearing is. It will not completely solve it but it may be one way to make it more accurate.

One problem I see is that one would almost certainly be forced to pause, especially if one uses 3.15 intervals. In the real world, one can expect more than a single person keeping track of it all as it happens so pausing could be used to fake 2 people working simultaneously. Not ideal but it might be a workable solution.

[Aquelarrefox]

Quinte: good job! very interesting. As i said, that is enought good to panning intersection, and get a enought good course to a perpenducular aprouch, with this also is posible with pericope readind of one or 2 distance estimate the distance of target in a defined position (using sen equa) for a blind shoot but im not sure how acurrate it would be in medium range. I should test it with a convoy (better oportunity)