Why don't targets zigzag?

[runyan99]

As in the title. Escorts zigzag in search patterns, but merchant vessels in convoy always run arrow straight courses until they are alerted by torpedo attack.

Is it not possible to program all ships to run zigzag courses, or has nobody bothered to do so? The Japanese always ran in some zigzag pattern in reality.

[The Fishlord]

As in the title. Escorts zigzag in search patterns, but merchant vessels in convoy always run arrow straight courses until they are alerted by torpedo attack.

Is it not possible to program all ships to run zigzag courses, or has nobody bothered to do so? The Japanese always ran in some zigzag pattern in reality.

I believe it's possible, I think RSDRC has them always zigzagging, I don't know if you've tried that or not.

[Suicide Charlie]

I'm running TMO + RSRDC and ships whether in convoys/fleets or alone will zig zag much more often. It seems like if your presence is even suspected they start zig zagging.

[Fearless]

Running RFB and RSRDC. Plenty of zig zagging when you're noticed.

[runyan99]

Sounds like you guys are getting spotted. The convoys should be zigzagging at all times, even before spotting a sub. Starting zigzag after the first torpedo attack isn't realistic.

[Carotio]

IMHO, the traffic should be scripted to have 50/50 zig-zag and straight running course, and that without your sub/uboat being discovered.
A straight run makes the ship/convoy arrive faster at destination, but is at higher risk. Zig-zag reduces the risk, but makes the voyage longer/slower. Hence a 50/50 part of each type.

That naturally forces more precise campaign scripting, but would make it worth while I guess.

[Fearless]

Sounds like you guys are getting spotted. The convoys should be zigzagging at all times, even before spotting a sub. Starting zigzag after the first torpedo attack isn't realistic.

Not necessarily. Slow convoys would loose too much speed and were then easy pickings. My believe is that convoys would commence zigzagging when instructed by the Lead merchant ship or by an Escort. In general they would sail straight in some kind of formation to keep maximum speed.

[Sailor Steve]

It sounds like we need to make a distinction. What the convoys do when spotted isn't zig-zagging, it's weaving, and that's something they didn't do.

After a sub has been detected the convoy would either a) change course away from the sighting, b) break up and run in different directions, to regroup later, or c) continue on course, since it takes time to reload torpedoes and it's already too late for any victims.

Zig-zagging is changing course along a baseline every every few hours. The whole convoy changes course in an attempt to be where submarines can't without surfacing. Very occassionally this will steer them right into the path of the waiting submarine. The biggest SH3 supermods have had their random layers changed to do this. I don't know about RSRD.

[runyan99]

Not necessarily. Slow convoys would loose too much speed and were then easy pickings. My believe is that convoys would commence zigzagging when instructed by the Lead merchant ship or by an Escort. In general they would sail straight in some kind of formation to keep maximum speed.

That's just not so. If you read the memoirs of the sub captains, every contact they made used a zig pattern, and analysing and timing that pattern was part of every approach and torpedo attack. There was no 50/50 about it.

The lack of zig plans greatly increases the ease of sinking large tonnage in game.

The only target I have read about so far that was not zigging was a Japanese sub on it's way into Rabaul harbor, with men in whites shining their shoes on the deck.

[Fearless]

Thanks for the clarification SailorSteve. :up:

[Fearless]

That's just not so. If you read the memoirs of the sub captains, every contact they made used a zig pattern, and analysing and timing that pattern was part of every approach and torpedo attack. There was no 50/50 about it.

The lack of zig plans greatly increases the ease of sinking large tonnage in game.

The only target I have read about so far that was not zigging was a Japanese sub on it's way into Rabaul harbor, with men in whites shining their shoes on the deck.

Location! Location! I doubt the convoy would've zigzagged their way out of Tokyo Harbor!

[Zero Niner]

Well, in my experience (TMO + RSRDC) I've seen both convoys & lone ships zig away from me, often when I'm already in position waiting to ambush them, resulting in me having to re-intercept. And I'm pretty sure I haven't been spotted either, as the way the AI ships react when they are alerted to my presence is a characteristic "weave".

[tater]

Sounds like you guys are getting spotted. The convoys should be zigzagging at all times, even before spotting a sub. Starting zigzag after the first torpedo attack isn't realistic.

Not necessarily. Slow convoys would loose too much speed and were then easy pickings. My believe is that convoys would commence zigzagging when instructed by the Lead merchant ship or by an Escort. In general they would sail straight in some kind of formation to keep maximum speed.

Real ZZ patterns were complex, and virtually all convoys would have ZZed the entire journey.

The patterns were not simple Z shapes, but almost sinusoidal looking.

http://i121.photobucket.com/albums/o222/tatersw/ZZA.jpg

http://i121.photobucket.com/albums/o222/tatersw/ZZF.jpg

http://i121.photobucket.com/albums/o222/tatersw/ZZM.jpg

The lack of any kind of realistic ZZing in SH is a major failing. Virtually all merchant shipping (warships, too) would ZZ in combat areas (which is everywhere given submarines). It can be added in the campaign layers, but it becomes unwieldy given the literally tens of thousands of added waypoints, not to mention the inability for the AI to really understand them.

"Organic" ZZ behavior would be a major game improvement. There might be a library of ZZ patterns like those above, and the waypoint would have a pull down to pick which pattern to use between waypoints (defaulting to "NONE.").

[Sailor Steve]

I'm glad somebody had actual documentation.

Wouldn't it be great to set up an intercept and watch them turn away at just the wrong moment? Or turn right towards their doom at just the right one?

Thanks tater.

[Fearless]

Thanks tater. :up:

[runyan99]

Interesting zig plans.

Also, some ships and groups used constant helming, by which the ships were always slightly turning to the left or right, around a base course. Even harder to target than a zig pattern with straight lines. Not possible to simulate in game, however.

I took a look at the mission editor today, and adding some form of zig plan is possible for all traffic by simply redrawing the routes for convoy and merchant traffic.

Possible, but time consuming, which is I suppose why it hasn't been done.

[DeepIron]

Possible, but time consuming, which is I suppose why it hasn't been done.
If I remember correctly, tater worked around with this a bit and the conclusion was that plotting *realistic* "zig-zag" patterns in the editor created a huge overhead for the game engine to cope with. There may have been other issues as well...

[Mush Martin]

I think theres still an issue of language

evasive routing
versus
tactical maneuvering

[LukeFF]

"Organic" ZZ behavior would be a major game improvement. There might be a library of ZZ patterns like those above, and the waypoint would have a pull down to pick which pattern to use between waypoints (defaulting to "NONE.").

That indeed would be great. Devs, please take note of this! :yep:

[Peto]

I've tried to create some zig-zag patterns in SH4 but, frankly, it involves so many way points that it over-loads my system. Not to mention taking about 200 hours to plot (by hand) a convoy from Palau to Tokyo.

It would be great to have to "figure out" a zig-zag plan and then dive on a projected point of intercept (in RL this could take hours to do). "How" to do it in game is beyond me though...

Great Charts tater! As usual :up:!

[runyan99]

I can understand if totally realistic zig plans create too many waypoints, but is there a happy medium? If real convoys changed course every 15 minutes, would it be possible to create 'lite' patterns where the convoy changes course each hour? Each two hours? Even this would be an improvement over the straight routes in stock.

[Peto]

I can understand if totally realistic zig plans create too many waypoints, but is there a happy medium? If real convoys changed course every 15 minutes, would it be possible to create 'lite' patterns where the convoy changes course each hour? Each two hours? Even this would be an improvement over the straight routes in stock.

You are absolutely correct. But even that is Hundreds of waypoints... Especially for slow convoys. Zig-Zagging is definitely on my wish list.

[tater]

The patterns in the above images are all for 1 hour, I believe. The angle shown, then the time in minutes.

I have a thread (search the forum for zig zags) that shows how to do it with the automated campaign editor. It makes a godawful pile of ZZs. You need to split the layers or it crashes the mission editor.

Also, the AI doesn't deal with it well. I did try "light" versions, but tthe ZZs literally need to be on the time scale of getting a firing solution, plus the travel time of the fish. Much longer and it's only good to make an end around slightly more difficult—cept the ZZ pattern slows them down. You NEED shorter time frame ZZ behavior for it to be effective. The japanese patterns shown above were the short time frame they were for a reason :D

tater

[joegrundman]

That is so interesting:know:

Evolution in practice!

Do you know what allied zigzag policy was like?

[seaniam81]

If i remember correctly from what my grandfather told me a officer on a British DD. The Allied Navies used different plans that could be changed hourly or daily or just when ever.

The convoy would have one ship who knew the plan and executed it. The rest of the convoy would have to do what the lead ship did. That lead ship would preform the ZZ at specific times on the clock. And this would negate the use of flags/lights/radio.

[tater]

Allied procedure was similar. They had a plan book of different ZZs and would execute them.

Note that in the IJN examples, the ships are back on base course every X minutes (certainly every hour). All the skippers would know that at the top of the hour (or whatever) they'd be back on base course.

[joegrundman]

I don't know if this interests you, but these excerpts show the USN end of war attack doctrine for dealing with these sorts of short time zig-zags

http://www.hnsa.org/doc/attack/index.htm

Some terminology:

critical range = distance target would travel in 7.5 mins - which is easy right? you all know the 3 min rule, so just double it and add a bit. 7 knots=c. 1500 yards. 10 knots= 2200 yards. This is the range at which you really must be moving from approaching the target to readying the shot.

target track: a line extended forward from the target along it's present course (ie the track the target will follow assuming no change of course)

distance to target track= distance from your submarine to this line

http://img507.imageshack.us/img507/2622/platexixpo6.jpg


Situation 1a Target has zigged in last 2 mins, target is on sub's beam. Distance to track less than 1000 yards

http://img150.imageshack.us/img150/6545/platexxjc7.jpg

Situation 1b as above but target on sub's bow

http://img150.imageshack.us/img150/2379/platexxiqi7.jpg

Situation 2

Target has not zigged in last 2 mins (and therefore will soon), distance to track less than 1000 yards

http://img150.imageshack.us/img150/2379/platexxiqi7.jpg

Situation 3

Target zigged in last 2 mins, distance to track more than 1000 yards

http://img209.imageshack.us/img209/5809/platexxiiimy7.jpg

Situation 4 Target has not zigged in last 2 mins, distance to track more than 1000 yards

http://img374.imageshack.us/img374/4851/platexxivbw6.jpg

[joegrundman]

You see i'd been following the previous threads, and i knew they had this short leg zig zag, but i never realised why they made it so tight!

So the allied convoys also used say 5-10 minute zig zag legs?

Man, this HAS to be in the next gen subim, but perhaps as an optional realism thing

[Sailor Steve]

I didn't know it was constantly so short either.

Cool stuff!:rock:

[Peto]

I remember a story from Monsarrat's (sp?) book Three Corvettes about convoying/station keeping in North Altlantic convoys. He said they were in fog and couldn't change station from the merchant they were using as a guide. So all night they held a constant distance and bearing on the that one ship--the only one they could see. In the morning, the fog lifted and they were the only two ships visible :shifty:. It took them the rest of the day to locate and rejoin the convoy.

Kind of off topic but a quaint antidote ;).

[Reise]

According to US escort of convoy instructions zig zagging not always considered effective

http://ftp.ibiblio.org/hyperwar/USN/ref/ASW-Convoy/ASW-Convoy-4.html


Zigzagging for slow convoys (speed less than approximately 12 knots) with a broad front is considered to be ineffective in avoiding attack of submarine as well as having the serious disadvantage in the loss of distance made good, and may result in confusion and straggling.

Zigzagging is considered to be effective and should be prescribed for high-speed convoys and slow convoys of relatively small numbers of ships in which the front is fairly narrow. Escorts conform in general to the zigzag courses of the convoy, but their stations remain relative to the base course.Of course as war went on most convoys were of a large number so would be broad at front
And most convoys in game less than 12 kts

Adding more zigzags can increase file size by massive amount too

If Japanese convoys always regulary zigzagged then there needs to be some form of course changes added

[tater]

Japanese convoys were all (with a few early invasion forces) small by allied standards.

If you read US submarine books, you'll see that the skipper almost always ends up plotting the ZZ courses of the ships before attacking.


tater

[joegrundman]

I have another question, then. When reporting the speed of a zigging Japanese convoy, would the speed reported be the speed of the individual ships, or the net speed along the base course?

[Mush Martin]

I have another question, then. When reporting the speed of a zigging Japanese convoy, would the speed reported be the speed of the individual ships, or the net speed along the base course?

No you tail and track the convoy
work out the ship speed
work out the base course around which
the zig zagging is taking place,
make an estimate of the formations
speed of advance along the base
course, and phone in the estimated
course and speed of the formation
along the base course.
tactical maneuvering zig zagging
wont effect this report
but strategic routing zig zagging
would through it off completely
so you stay with em till the
turn and phone it in and hope for the
best.

[tater]

US boats would almost never radio a contact report though—only if they were completely unable to attack, and even then, I'd imaging they'd let the convoy get away a little so if they were DFed it might not be linked to the convoy/TF.