TDC, PK, manual targeting, corrections.

[Sniper297]

Playing around with CapnScurvy's OTC mod, set up my own mission so I already know what the target's actual speed and course are. Also playing with map contact updates on as "training wheels" so I can check the accuracy of my range observations and measure the true AOB.

Couple things about manual targeting, bearing is a no brainer and impossible to screw up, point the scope at the center of the target and there's the relative bearing. Range is more iffy even with OTC especially at longer ranges when you can't actually see the tops of the masts. AOB forever eludes me, difference between port 5 and port 10 takes an eye better than mine. Fortunately if I have the PK on it automatically tracks range - bearing - AOB and updates them with each new input.

One thing I'm missing, and a google search don't mention it one way or the other - what about speed calculations? If I have an exact range and bearing and take another perfect range and bearing X minutes and seconds after the first, I can run a course track between two points, and using the time it took for the target to get from point 1 to point 2, come up with a really close solution to the actual speed of advance.

TDC is an analog mechanical computer rather than the electronic digital gadget I'm typing this on, but if it didn't have a circuit to calculate speed automatically and correct it automatically based on each input - update it really should have. Theoretically I should be able to get a range and bearing, wait 5 minutes and input another range and bearing, the TDC should be able to figure out just from simple geometry and clock, using the difference between the two points and time elapsed, (1) target speed and (2) actual AOB. If it worked the way I think it should have worked, I should be able to leave speed and AOB at zero, input two range and bearing positions, and the TDC would give me something in the neighborhood of the actual speed and AOB without mussing its hair.

Anyone know the actual dope on the WWII TDC? Did the developers get this wrong and leave out some actual capabilities?

[Longknife]

I am not 100% I get what your asking so I will answer what I think you re asking

The TDC is a mechanical device. Think of it like an abacus. It's keeping track of the data inputted much as an abacus keeps track of the sums entered but also like an abacus it takes a cognitive element to interpolate the data.

I am old enough to remember when calculators hit the scene & they were a marvel of the 60's. You are asking your 40's vintage TDC to do some of the same functions.

[TorpX]

Originally Posted by Sniper297

One thing I'm missing, and a google search don't mention it one way or the other - what about speed calculations? ....


Anyone know the actual dope on the WWII TDC? Did the developers get this wrong and leave out some actual capabilities?

Speed had to be manually input, just like the others.

There are probably a number of reasons why:

• 1. At the start of an approach, you would want to put in an initial guess. If you see a merchant chugging along, and see in the RM that it has a top speed of 12 kn., you might dial in 10 kn. and start with that.
  2. You might need to make a 'snap shot', and estimate speed based on bow wave or such.
  3. If the TDC rigidly calculated speed based on the last 2 positions entered, they could still be in error, if the target has zigged in the meantime.
  4. I think there had to be the option of the tracking party overriding simple calculations based on their experience.

Basically, the same goes for the Target Course/AoB. In theory these could be calculated if two consecutive positions were accurately known, but in practice, you need to estimate AoB and make manual inputs.

There were different models of TDC used in the war. I don't know all the details, but at least some were made so that as new data was dialed in, the error (or difference) between the observed data, and the TDC calculated value, could be seen. In this way successive observations could be used to refine the firing solution, and the crew could see the difference between the observed data, and calculated data get smaller and smaller.

I should also add, in the real-life TDC the PK was always 'on'. There was also a mechanism which showed the 'distance to track', but maybe not all models had that feature.

[Sniper297]

"You are asking your 40's vintage TDC to do some of the same functions"

I was born in 1953, so I'm also old enough to remember when electronic calculators were the latest high tech. I was an aviation ASW tech in the late 70s so I understand the technology of mechanical tracking systems, and the WWII TDC could easily have had the same functions.

Near as I can tell from the documentation though, that feature was not in the TDC;

http://archive.hnsa.org/doc/tdc/index.htm#toc

Because it was instead in the mechanical plotter, which SH4 doesn't even hint at. TorpX mentioned distance to the track, which near as I can tell was also incorporated into the mechanical plotter. Hard to find info on the plotter - I worked on the PT-396 plotter from the P-3 Orion and the ASA-13 plotter from the SH-3 Sea King, both were top secret at the time so finding details on those is also difficult. They were 60s technology but both were mechanical, with a tracer moved under a rolling sheet of translucent plastic burning lines and target marks on the underside.

Here's the only picture I can find of the WWII sub plotter table;



Under the sheet of glass you can just see the mechanical arm which is moved by small motors based on inputs from the TDC, gyrocompass, and pit log. At top just left of center you can also see the bottom of a repeater dial linked to the sonar console up in the conning tower, this gadget is down in the control room.

Game doesn't even hint at this technology let alone simulate it, the auto map contact update is probably the closest we'll ever get. What would be great is if some genius modder could reprogram the ingame map to display targeting and tracking based on input from the player instead of choosing either automatic full perfect tracing or no tracing at all.

[CCIP]

Yeah, from what I've seen and heard on the subs I visited, the TDC came with a tracking plot which was used for targeting solutions. I think in SH logic, it's not so much the TDC itself as the in-game attack map that replaces it, probably for gameplay reasons since it's a lot more intuitive than a linear plot, especially if you're playing with map contacts.

Interestingly, one of the subs I've been on where I was told about the paper plot was the USS Pampanito, and IIRC that was the sub that the SH4 devs visited when building the game, so I thought that the TDC was modeled on the one on Pampanito, except for the plot.

[TorpX]

Originally Posted by Sniper297

What would be great is if some genius modder could reprogram the ingame map to display targeting and tracking based on input from the player instead of choosing either automatic full perfect tracing or no tracing at all.

Agreed.



I don't believe subs had the full mechanical plotter as you describe it. I think there was a plot table with a dead reckoning indicator, that would show the position of the sub (not sure if all subs had this). It wouldn't be directly linked to TDC, but rather both the TDC and DRI would receive input from the pitometer log and gyro compass. The targets would have to be plotted by crew.

Furthermore, the TDC was developed before Radar. The 'normal' method of approach would be to close submerged, and make periodic observations, by periscope. This means the tracking party would have to figure out when and where the zigs occurred, and iron out any inconsistencies in the plot. The process could not be completely automated; they had to be able to make changes.



P.S.

I looked at some of the diagrams in N. Friedman's sub reference. He shows a few examples of the conning tower layouts. At it's last refit, Haddo had a Mk. 4 mod 0 TDC, and a DRT (dead reckoning tracer?) table in the back of the compartment. As they were close together, it is possible they did work together in some fashion. By war's end, the CT's were very crowded.

Early TDC models took up more space, and were located in the control room. Experience lead them to design a more compact unit to put in CT, so skipper could see both plot, and TDC data, and the TDC could get inputs from Sonar/Radar. I wish we had the nitty-gritty details on all this.

[Sniper297]

Off topic, but what in the world is with the pictures? I can post a picture by simply using CTRL-C to copy an image, then CTRL V to paste the pic directly into the post. But the pictures later mysteriously disappear, at first I thought it was imageshack, but pictures not hosted on imageshack are also MIA. So I started copying the URL and using the Insert Image button at the top instead. My second post in this thread (#5) had a picture of a plotter in it, now it's gone.

I'm looking over the FAQ and rules, I don't see anything except a restriction on posting X rated stuff. Is there an unwritten policy about image size, dimensions or kilobytes?

[Sailor Steve]

I'm not sure why you would be having picture problems. Other pictures on the forum are showing up fine, and no, there are no size restrictions I'm aware of.

I use PhotoBucket myself.

[CapnScurvy]

PhotoBucket for me too. Copy/paste the link provided into the SubSims Image editor. I usually use an 800x680 image size.

However lately, I've seen a lot of add issues slowing down the process on PhotoBucket. I see their offering an "Add Free" process for a price.....but I'm not biting.

[Sniper297]

I had no end of irritation with imageshack and photobucket, so I gave up and made a couple of "shared with public" facebook albums for pictures. Possibly it's on my end, does anyone see the picture in post #4 (my second post in this thread where it says "Here's the only picture I can find of the WWII sub plotter table" )?

Two ways to do this, copy image, paste image right into the editor window;



Or copy URL and paste into the Insert Image tool window;



And it works, but when I look again a few weeks or months later the image is gone, no link, no evidence it was ever there. I don't have this problem on other forums.

[les green01]

i dont see a pic in post 4

[Pisces]

I've never heard of being able to insert images into a post by copy/pasting it on Subism.com. It always needs to be uploaded to a online location, and linked to it by url. And added into a post by using the [img][/ img] tags (there is a button in the full editor for it). Or by using the "Manage attachments" button in the full editor, and upload it to the site via a pop-up window.

[Sniper297]

Doesn't matter how I do it, the pictures are there, I log out and disconnect from the internet, reconnect and look again, still there. Go back a few weeks or months later and they're gone without a trace. I recently edited this thread;

http://www.subsim.com/radioroom/showthread.php?t=211613

to replace the two images that were missing, they were there on March 1st and missing by March 24th. This is the first time I've had images vanish on the same day, but however I add images there's something screwy going on more often than not.

[TorpX]

Originally Posted by Sniper297

Possibly it's on my end, does anyone see the picture in post #4 (my second post in this thread where it says "Here's the only picture I can find of the WWII sub plotter table" )?

I never saw any pics in #4. I thought maybe the problem was at my end. Last week, there seemed to be a lot if images missing for me.

*I think*, the plotting tables they used, had a light tracer move underneath the paper, but the crew actually penciled in the tracks. The tracer corresponded to the sub's position; they still had to rely on periscope/TBT/Radar data furnished by others for marking the track of target(s). I can't remember where I read this, though.

I skimmed through the TDC manual at HNSA.org. There is certainly a 'distance to track' dial or readout on the Mk. 3. They don't really give a good, close-up view of the dials, but it's there.

The don't really say much about the 'sound bearing converter', either.

[Sniper297]

Well, I don't know. The two pics I posted in #10 are still there, and naturally I can't find the one of the WWII fleet boat plotting table or remember the exact search term I used. Google is well named because that's the number of useless unrelated hits it returns.

One problem in finding photos - when I was in the Navy there were many restrictions on even the possession of a camera, and an AX had a lot of background checks and security clearances involved, "burn before reading" all that stuff. I got out in 1982, and was rather shocked to pick up my first Tom Clancy novel only a few years later revealing a lot of the classified info I knew when I was on active duty. Apparently it was declassified and I hadn't heard about it.

WWII was undoubtedly the same, all this stuff was probably so top secret there was very little in the way of documentation or photos available after it was declassified. Mark 14 with the Mark VI exploder was a good example, so secret that when the war started all the submariners tasked with maintaining, prepping, adjusting and firing the torpedoes were scratching their heads trying to figure out a new system nobody ever heard of with no manuals or training. SNAFU.