Determining course of contact that is "smoke on the horizon"

[pythos]

Finally got Steel Wolves and SH5 working on my rig. Now this mod has NO map contacts, and this is proving troublesome when it comes to contacts that are "smoke on the horizon". I try to plot the position, but of course all I have is bearing. Now, I have clicked on the WO's report, and that gives a range....this is nothing less than cheating. Also it seems the mod has made this unreliable. I had a contact go from 18KM to 7 in less than a minute (it was a boat, not a plane). When I got multiple reports and plots, the course of the contact was.....ludicrous. I searched here for good tutorials on plotting contacts with no map up dates, but could only find ones with updates, and were for older versions of Sh. Could someone help, or at least point me in the direction for a tutorial, or what have you concerning tracking distant contacts.

[Jaystew]

Suppose you are heading due north and your heading is therefore 000. Take the contact's bearing from your ship. Suppose its at Bearing 060. If you want to make an intercept, first start with pure pursuit by changing your heading to that of the contact. Make heading 060.

There are 3 possible outcomes. The target can be heading...
Directly toward you (Unlikely)
Directly away from you (Unlikely)
On a different course than your course. (Most likely)

Once on that heading and at a steady speed. 10 kts is a good long range intercept speed. Note the time exactly. Note your position on the map exactly and note the relative bearing of your target exactly. (Be aware you do not need to know exactly where you are on the ocean only exactly where you are relative to each tracking measurement you are about to make.)

Make an X on the map noting your subs position. Draw a line of bearing out from that spot and extend it 30km.

At 2 minutes note the apparent bearing of the ship on the horizon. If the ship is to the left or right of your bow you can rule out that it is heading directly towards or away from you.

If the contact is still on bearing 000 and simply smaller or you've lost contact it was moving faster than you and opening distance. If the contact is larger but on the same bearing are your pursuit it is closing. It have may detected you and be on an intercept course. Likely a warship. The last possibility is that it is moving directly away but slower than you sub so you are gaining on it.

In the most likely situation the contact will be either right or left of the bow a few degrees. Remember you matched your heading to the bearing of the contact and are on heading 060. Suppose the contact is now at bearing 002.

The only thing you can conclude is that the target is heading somewhere between 060 and 240 and that it is moving.

So again at 2 minutes note that the contact is now at 062. Maintain your heading of 060 along the original bearing. Measure out where your sub would be from the original X and make a new X. From this new X draw a line of bearing out 30km.

Repeat the process at 4 min and again at 6 min. As you take more bearing measurements. Assuming the target maintains a straight course you will very soon determine the range within a few hundred meters. You will also be able to determine the targets course within 10 degrees.

That should set you up with where you need to go in the beginning.

[Sailor Steve]

Brilliant explanation! :sunny:

[pythos]

Wow!!! That is the BEST explanation I have seen concerning this perplexing problem. This should be pinned. Gonna give it a whirl tonight Thank you.

[Jaystew]

I didn't even think it was that good but I'm glad you guys like it. Here is part two.

http://i.imgur.com/6WNbGcQ.png

The angles are not proper and only exaggerations but technically correct. You can infer alot from the angles without them being correct. Such as approximate distance and approximate direction based on where your best guess position is.

For example, so the mid range of where your plots are put the target at 15 km from your sub which is probably right. More right than if its in the range of 5km or 25 km logically if it is just on the horizon is must be in visual range which rules out 25km and if it is so small you cant make out what direction the bow is facing then it must be greater than 5km. So 15km it is approximately. Now every 2 min you can draw an approximate line between points about 15km from your sub along the lines of bearing from your visual observations which will be accurate. This will give you a general direction of travel. If you are very accurate with your time and speed keeping you will have a course of your target within 10-20 degrees with only 3 measurements. The more measurements the more accurate the inferred conclusions derived from the data.

Some considerations...

The target is moving so even if your measuring is accurate it will not explain why everything does not exactly line up. The target may also be zigzagging likely and this will add to variability in your best guess. The conclusions will derive from the best observations which will be the last 3 you made, but do not discount the previous observations and recording as they will serve to confirm direction of travel and/or conflict with your course plotting.

Also. The target may change course. If they have detected you or on the whim of the captain. In which case you may not longer need to make observations in the case where they are heading towards you to attack, or where you will need to continue to observe to again determine their new course. With even more observations you can determine their course sufficient to match it and then run parallel.

Once parallel you can increase or decrease speed to determine the speed of your contact. This will be in lesson 3 which I'll put together laters.

Oh yeah, use the nomograph to determine how much distance you travel at 10kts in 2 min. Knowing this will help you to know the larger triangle problem.

Here is a link to the grand tutorial...
http://imgur.com/a/EstMH#0

[pythos]

After reading the first answer, I was thinking to myself how great it would to get a graphical explanation of the process, and lo and behold!!!
This is really something that has baffled me for a long time. This latest addition REALLY helps. Now I get it the point where the bearing lines intersect that gives the position of the contact!!!
This is gold.
Thank you for this, and this still should be pinned.

[Jaystew]

Well you got to be careful. If your contact is a stationary contact, like a tree or a lighthouse then yes that is true. Which of course is how you determine a "fixed position" on the map when you are close to shore and know a position or can very closely estimate a position such as a lighthouse or part of a port. You get two or 3 lines of bearing which are just straight lines taken at a different time and where they line up is where the object is, and therefore you can infer where your position was at one time from that. Much more accurately than even celestial navigation which will calculate you down to the nearest 1-10km in the best of situations. Position fixing by known navigation points will take you down the nearest 10-100m in the best of situations.

If your contact is moving either in a steady course or in a random or semi-random course it will be impossible to plot the position exactly using just these observations. Also the target could or may be changing speed. Which could also throw off your calculations.

Im going in game to make a better graphical example.

[Defiance]

Very neat concise and easy to follow

Bravo Jaystew :yeah:

:salute:

[THEBERBSTER]

Hi Jaystew

How were you able to import that size picture?

Every time I try to import a large picture it reduces the size down.

Peter

[vdr1981]

Great explanation Jaystew . :up:
However, it's pity because most of the players will be more interested in how to enable arcade minimap and/or GPS/map contacts updates rather then actually learn about some real life WWII procedures used by submarine captains...

[pythos]

Yea, I actually dislike feeling the need to turn map contacts on. I think I am going to turn on ONLY the hydrophone ones as there is no "report closest merchant" opposed to "nearest contact" or "nearest warship" as if there is a warship around "nearest contact" will report the warship over a merchant.
I WANT to go to real navigation and mostly no contacts, once I understand what I am doing. LOL

[Jaystew]

I have hosted the large image file on imgur. Its free and they allow you to do unlimited upload of png/jpeg files. You can sort them into albums. Etc. I think it is a very good free service. I use it to host my maps as well and also the above tutorial.

Here is the tutorial with a sort of slide show please check it out and give me some feedback.
http://imgur.com/a/EstMH#0

Also my maps so far I've completed 5 of them, they are huge, feel free to download the full resolution.
http://imgur.com/a/ssMsk#0

Also a link to that thread. http://www.subsim.com/radioroom/showthread.php?t=213138

[Jaystew]

I think for me when I'm on the open ocean I don't bother checking the hydrophone as often as I should. But in the early war it is definitely worth checking when going through a 75-50km chokepoint rather than doing a visual sweep because you can cover so much greater area. I also dont think its a bad idea to do it every 2-4 hours while on patrol or in a high risk area.

Knowing that there is a contact to the south when it could only likely be an escort patrol such as in the shallow waters or near a port, definitely helps make good navigation decisions and avoid the enemy. Once in visual range its sometimes hard to get out of a slow sticky situation with escorts. Especially in shallow shallow shallow water!

As the war goes on it becomes more and more important as surface travel is either limited, dangerous or almost impossible. More destroyers and aircraft in 1940 make for minor irritants to surface travel, in 1941 especially after the USA enters the war it becomes even more limited. In 1942 I think its dangerous to be on the surface not just during during the midday but even at night. In 1943 with all the aircraft if you get spotted or detected by their radar they will relay your position and if you are not in deep water the destroyers will ASDIC you to death and DC you and use hedge hogs boom boom boom. Not only in 42/43 do you not have the advantage but even with the schnorkel until the Type XXI in late 44/45 does the Kriegsmarine have the advantage again and at that point the war is already lost.

[Jaystew]

Great explanation Jaystew . :up:
However, it's pity because most of the players will be more interested in how to enable arcade minimap and/or GPS/map contacts updates rather then actually learn about some real life WWII procedures used by submarine captains...

I think the trig throws people off because you can use trig on the fly to help with angles and shooting solutions. But a lot of the intercept data is geometry rather than trigonometry. I was much better that geometry than trig and so I stick to what I know from geomergy. Algebra easier than calculus etc.

I know that A^2 + B^2 = C^2 in a right triangle from geometry. Now that works for right triangles, those with a 90deg angle, which just so happens to be exactly the angle you want to attack your torpedos with on the hull of a target. So I say screw trig. I dont have time to do trig in the boat while lining up the ship, and keeping the boat in order, checking out asses for destroyers making sure there are no AC etc.

Even the best captains under that level of stress and daily grind, do you think any of them would want to put their trust in complex mathematics when the KISS keep it simple stupid principal applies?

Bologne, they want to sink the the ship and go home. Just think one complex calculation with a single error could throw off the torpedos. Why use complicated stuff when you could use easier stuff. Of course if they had access to GPS they'd probably use it too but bah they didn't so why would we in a "simulation" LOL turn on GPS cheating. Come on guys. What kind of Skipper are you, are you on a 3 hour tour with Gilligan?

Simple geometry easier faster to calculate some in your head even.

A+B=C My favorite right triangle is 3^2+4^2=5^2
9 + 16 = 25

[DieReeperbahn]

A+B=C My favorite right triangle is 3^2+4^2=5^2
9 + 16 = 25

I always liked
A^3+B^3=C^3 :know:

[pythos]

Well I was finally able to try this. I discovered to my chagrin that the line of bearings I made did not intersect at all. Instead they fanned out. This gave no useful data at all other than the contact was moving. I then turned contacts back on, and tried this again, and saw that the termination point of the lines of bearing did kinda follow the course of the contact, but were many km off. Still need help here.

[Jaystew]

Can you show or tell us list us your observations...

Sometimes the lines of bearing do fan rather than converge but this indicates the target is move faster thank you or the course you are using against their course is too wide or even perpendicular to their own.

Lets debug it.

[Jaystew]

I always liked
A^3+B^3=C^3 :know:

I dont get it. Where does this calculation help you in submarining?

[pythos]

It was a destroyer, and what you said is what I was thinking, the contact was going fast. So does that mean this method won't work on fast moving contacts? I got the initial report, set my heading toward the contact (smoke on the horizon), set my speed to 10 kts, marked my point, and drew a 30km line. Waited 2 minutes, and placed the next mark, I forget the bearings given. As I stated though, the lines fanned out, and the terminiation point of the lines if a line was drawn from point to point would almost parallel the course of the contact. (recall I did have map contacts on).
Hope this helps.

[Jaystew]

Im having trouble visualizing what you were observing. There are times when triangulating is going to be difficult or impossible. If the contact is moving away at high speed. A good thing for a destroyer, you would typically see a converging of those line of bearing farther and farther away.

For example if you drew a circle every time around the location where your last 3 lines of bearings get closest to each other and then each time you did that those circles would move gradually would be farther and farther away even though you should observe the lines of bearing being closer and closer together.

If they are starting to fan out and the tighten up that would to me indicate a destroyer running perpendicular. One running parallel to your own subs course. Would be relatively easy to spot so long as you are both heading in the same direction, if you are heading in opposite directions the angles between the lines of bearing will get smaller and smaller.

Maybe we are making this too complicated. If you have a visual contact to make the general direction of travel as simple as possible observe the smoke from the ship. Think of the ship as a candle, as you move a candle from left to right the smoke is highest in the left where it originated from and lowest at the point closes to the flame. If that smoke is on a steady rise without a trail either on the left side or the right side, that ship is either coming towards you or heading away or stationary. If it is larger in 2 minutes its coming at you. Let me make a few more diagrams to aid you and then we'll see if we can figure out how to determine the course of a fast moving target.

If its pressing at 30 kts or so you may not be able to exactly nail down its course without trig but with practice you should be able to guess it within 10-20 degrees based on the sight picture of the angle on the bow and your ship's current heading. Meaning if you are heading North and you see a car traveling from left to right which direction is it heading? It is heading East. Now suppose you are parked at 330 and when looking at the AOB or angle on bow it appears to be at 60 degrees of the right side, so you can fully see the bow and not see the stern, so take a guess at which angle you are seeing. If you are at 330 and the contact is heading left to right and you appear to be at AOB 60 Right then it must be heading about 030. It is a lot of guessing and you wont always be right. Which is why you make more than one observation.

The closer you get the easier it is to make accurate guesses, and shorter the torpedo run has to be. As long as you are in deep water there is no benefit to attacking beyond 900-1000 meters and if you can get inside between 400-800 meters. Do it.

One torpedo shot from the hip at that range at high speed almost always hits with enough time to launch a 2nd one on a modified gyro angle if the first one fails to detonate.

[DieReeperbahn]

I dont get it. Where does this calculation help you in submarining?

I'm joking :D It's Fermat's theorem...no solution.

[finchOU]

If that smoke is on a steady rise without a trail either on the left side or the right side, that ship is either coming towards you or heading away or stationary.

Maybe a different example? Smoke in SH5 is effected by the current wind condtitions, therefore Smoke is an indication of wind direction and intensity but not ship course.

[Jaystew]

Lol what weather? I typically have 0kts for wind speed. So you can't determine if a ship is heading from left to right or right to left because of the weather on your configuration? Hmmm interesting.

[pythos]

Second attempt, this time with a freighter, the contact was moving slow, on a heading of 045, my initial contact was 360, then 2 minutes it was 359, next 358, next 357. The contact was moving to my left, however the lines of bearing were still fanning out. Something is missing in this tactic. I am trying to find out what. There had to have been a way of using simple bearings to figure a contacts course, and I think this method is close, but there is a step missing.

[Jaystew]

Looks to me you are doing it exactly right. If your contact is heading 045 you determined the course how?

360
359
358
357

What was your heading originally? My guess would be you were heading between 270 and 360. The reason I say this is because this is the only angle of approach where the contact heads 045 but the angles begin to spread to the left, and only if you are moving faster than the target, say 6-10 knots.

What was your heading originally when the contact was at apparent bearing 360?

[pythos]

Oh, I had map contacts on to see if the bearing lines were indeed intersecting where the contact was. They however fanned out along with the target (note I was getting my bearings from he WO, and using only the Bearing data, ignoring the map contact). Because of this I was able to determine the course of the contact after I had a go with the lines of bearing.
Contact original bearing was 090, my boat was on a East heading. I steered the bow toward the smoke, which took me on a northerly heading, contact at 0 degrees, and first mark and lines made, after two minutes, bearing 359, next two, bearing 358, ect.

[Jaystew]

I'm thoroughly confused. Take a screenshot. Were you able to determine what you set out to determine?

[pythos]

Try explain to me the point of confusion.

No, I was not able to have the method determine the course of the contact. The bearings did nothing but follow the contact. I was already planning on making a post with screenshots. :)

[pythos]

I did my best getting some shots of what is happening. My original course is the outlined set course line visible in this first pic. I was alerted to smoke on the horizon. At the time of this shot I had turned the boat to head toward the smoke. My first X is drawn
https://www.flickr.com/photos/29482148@N05/14276649799/in/photostream/
The next shot is where I drew my bearing line based on the report (NOT the contact drawn on the map. I am ignoring that for this exercise)
https://flic.kr/p/o358bx
Two minutes later I draw my next line
https://flic.kr/p/nKAvKz
Then the next two minutes I do the same.
https://flic.kr/p/o4Rt2r
As can be seen the lines are fanning out, they are not converging. The target was not going fast. I was drawing the lines out to the edge of the bearing indicator, and the termination mark in no way represented the contact course.

I wonder what is going wrong here.

[pythos]

For some reason Flickr is not allowing me to share pics that I have marked as public. I will figure it out later. kinda pissed at this. (the flickr thing, not the issue of this thread)

[Depaor1970]

It will rarely be the case that these bearings taken from your ship moving at 10 kts of another vessel moving at speed (say 5 -35 kts) will ever intersect. What jaystew is showing you is how to interpolate the direction of travel and with experience doing this how to guesstimate an initial course and approx. speed for your future target. The turn towards the bearing and speed to 10kts ( I normally go to 15) are all good initial actions and certainly within a few minutes u can determine approx. direction of travel and whether that contact is moving fast or slow. If that bearing to the target is steady and it is getting bigger in your sight picture but is travelling fast then its time to get the hell outta the way lol or at least prepare a good sternshot. In general though it will be a slowish moving merchant. Jaystews description of how he guestimates the initial range is important. This is what we in the trade would call "the seamans eye", it develops over time. In game I think it is similar that the more you practice this initial guesstimations the better u will learn to determne wheter it is an appropriate target you can intercept. Keep trying is my advice but do not look for a perfect solution, remember to use the visual clues available to u through uzo/binos. Is the smoke fainter or stronger, can I now see mastheads or silohette of a ship. From what I can see you are so close to getting to grips with this, just trust your instincts a bit more. remember this will not be the information you will fire your torps on this is just initial can I intercept, which way is it going and how fast and is it a viable target for me. Keep the faith Herr Kaleun.:yeah:

[pythos]

Oh don't worry, faith is not lost, I love this sim no matter how frustrating it is at times.
I Jaystew's description is very promising, and your statement about the "seaman's eye" helps a lot also.
I have for the longest time how the crew of any vessle was able to judge distance and course of a distant contact. What you say makes sense.

This sim makes it all the more impressive how the crews of these vessles were able to do as they did, without the marvels of GPS, and other such things. It is really incredible.

[Depaor1970]

When you initially get the observation and take bearing and turn on course, might be worthwhile to drop down and try to get a range approximation from the sonar guy. Problem with this is it slows your interception and u may lose the contact. The way I try is an aggressive burst towards that contact. Watch the direction his bearing is going and follow it or put ur course left or right of it, e.g his bearing has been drawing left 090, 085, 080 at each observation then I would steer maybe 060 and go to flank/full between observations. Same if bearing is drawing right e.g 090, 095, 100 then I would steer maybe 130. If after a period of time I am not any closer e.g 45 mins to 1 hour then I would probably give up as I am just wasting valuable fuel on a fast moving contact that may kill me or be able to outmanoeuvre a long range torpedo shot. I note where I came across the fast mover especially if I think its a fast moving high value target and may check this area out again in a future patrol to see if I have better luck. Happy hunting:arrgh!:

[pythos]

I am now being a sadist. LOL. Giving a try with real navigation with no map contacts (accept hydrophone) Hope my keel is strong. LOL

[Pisces]

If you search the forum for "4 bearing method" (in silent hunter 3, 4 and 5) then you'll find method descriptions, including some movies, on how to determine target course based on bearing alone. This is basically what you do with only looking at smoke on the horizon. But you really need to figure on what angle the smokestack is hiding.

Looking at 1 degree changes over 2 minute time steps is not going to show anything. Moste likely your boat was turning and bouncing on the waves. Be more patient and consider time intervals in the order of 15 minutes or longer. Then you'll clearly see that the bearing fans diverge. The difference between 3 bearings can be used to determine target course. But if you move yourself then it get's very tricky, and you need more bearings.

This is a tool I made myself for this sort of tracking:

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

[Jaystew]

I just had some major computer issues to deal with sorry I wasn't abandoning you. Have to re-install SH5 and basically my whole computer setup. Ugh. I hope your AOB/bearing problems are becoming more clear.

[pythos]

Found the method. Reading it now. Oh man has SH 5 taken on a new level. This is gonna suck at first, especially dealing with the CTDs, but this promises to become as close to real as one can get with this sim.
You all kick ass with the mods, and tutorials for this too often maligned sim.

[pythos]

Then...I find in the tutorials menu of the main menu, a 4 bearings tutorial. Giving it a shot now.

[pythos]

That tutorial is very good, I now have a good grasp of this method. Giving it a try in mission.