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!

[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.



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

[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 .
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]

Originally Posted by vdr1981

Great explanation Jaystew .
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]

Originally Posted by Jaystew

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