Not knowing my OWN position?

[epaga]

Hi,
A thought just struck me: I know there's a realism check box for not showing targets on the map, but my own position is always shown perfectly - this of course was not the way it "really" was - they didn't have GPS back in the day or magic updating maps. So...

1) Is there a mod that enables you to turn off your own position marker? (Didn't find any)
2) If so, or if there was, how would you calculate your own position?

Thanks,
epaga

[nfitzsimmons]

Originally Posted by epaga

2) If so, or if there was, how would you calculate your own position?

That's the problem. You can do celestial navigation in real life, but so far nobody's worked out how to do it in the game. Due to the cylindrical sky projection it may not be possible.

[epaga]

Bummer...hmmm then maybe an alternative would be to have your position be updated by "mouse click" of an action, but only to a certain degree of accuracy, say, within 1 nm or so? The same should be for radioed in contact reports, as well, which may already be modeled.

[anthrax]

Actually, It was pretty reasonlble to be able to know the location of your submarine accurately.
Fleet type submarines had a underwater log system that could accuratly track the movement of the submarine even when it was submerged. This system was accurate enough for fire control purposes. The data from it was then fed into the TDC so that the "position keeper" could keep constantly create an accurate firing solution on a target.

[Payoff]

Some folks do this with SHIII. I think they use control + Left mouse on the map to pinpoint their location to simulate a sun/star shot, but only in clear weather. No cheating.

[epaga]

Originally Posted by anthrax

Actually, It was pretty reasonlble to be able to know the location of your submarine accurately.
Fleet type submarines had a underwater log system that could accuratly track the movement of the submarine even when it was submerged. This system was accurate enough for fire control purposes. The data from it was then fed into the TDC so that the "position keeper" could keep constantly create an accurate firing solution on a target.

Was this system used for navigation as well, not only for moderately short-term firing solutions? Also, I always thought the PK didn't take into account any of my own movements...guess I was wrong, wow, that makes it an even niftier invention then I thought.

[Sailor Steve]

The only thing the 'log' could do was compute speed according to propellor revs. It couldn't account for currents, which could move you forward, backward and sideways without your ever knowing it. Sun and star sightings had to be taken every day. In overcast weather it was quite easy to find yourself many miles off course. The longer the bad weather lasted the more 'off course' you would get.

[anthrax]

The underwater log system could accurately measure "speed" and "distance" traveled. It measured "dynamic pressure" caused by movement of the submarine through water.

You are right that it didn't "take into account of currents" so this couldn't be used solely for long range navigation. The speed however was still useful information for navigational use.

As for its uses in fire control.
The "speed" measured by the "underwater log system" + the "course" measured with the gyrocompass were the only imputs that were automatically fed into the TDC.

The "Postion Keeper" constantly calculates the position of the target in relation to the submarine. So in effect, it was definately was capable "knowing where the own ship location was. The PK required at least the following 5 inputs.

2 automated imputs that were constant fed into the TDC.
ownship course from "gyro compass"
ownship speed from "underwater log"

4 inputs estimated or measured by the subs crew at least once.
Target course (AoB) = from estimation of plotting method.
Target speed from estimation or plotting method.
Target bearing = From observation on preriscope.
Target Range from Standimeter (which required a estimation on target height) or from radar.

2 outputs where constantly shown at the observation locations. (the other could be read of the TDC)
Caculated target range.
Caculated target Bearing.



Back to the original question, of whether you should know your exact location. For the purposes of Firecontrol, Yes, its reasonable to know and IRL i beleive there was device called the " Dead reckoning tracer" that could automatically plot ownship location onto paper.

[Snowman999]

Back to the original question, of whether you should know your exact location. For the purposes of Firecontrol, Yes, its reasonable to know and IRL i beleive there was device called the " Dead reckoning tracer" that could automatically plot ownship location onto paper.

There was a DRT in the conning tower and there still is (or was in the 1980s) in Control. The modern Geo Plot is kept on top of it at BS. In normal steaming the nav chart is laid over it and the "bug" is lit and shines through the paper.

The DRT is a waist-high cabinet full of gears and sychros. It has a plate glass top and two internal sliding bars, sort of like the guts of an Etch-A-Sketch, are driven by the clockworks in precise directions and speed. At their intersection is a small device carrying a tiny light pointed up through the glass--this is called the "bug". There are cranks on the exterior to drive the bug to any location. This is useful when a nav chart is over the glass and the bug has to be slewed to the location of a new fix.

The DRT was reset after every fix, either celestial, radar, or visual crossed bearings if near a landmark. It then took inputs from the speed log and gyro compass to dead-reckon current position. It did not account for wind, wave, or current, so it slipped over time. Every prudent navigator never fails to grab a fix in EVERY case presented. Not knowing where you are against a lee shore has been a CO nightmare for thousands of years.

As for fire-control and knowing where you are, who cares? If there's a landmass or shoals nearby mark them, but the FC solution is all relative anyway. A modern geo plot is done on blank tracing paper. You know the target is X yards away at Y bearing. Pick a blank piece of paper and mark him those coordinates away from the DRT bug. Lat and long don't enter into it. Torpedos don't speak lat and long.

[Sailor Steve]

Originally Posted by anthrax

The "Postion Keeper" constantly calculates the position of the target in relation to the submarine. So in effect, it was definately was capable "knowing where the own ship location was.

I don't quite understand. The Position Keeper is only as accurate as the information fed into it, so it should go to pieces if the target changes course while nobody's looking. How does that make it know where it is (the GIGO principle comes to mind; even a modern computer doesn't have that ability unless data is updated constantly from a GPS system).

[perisher]

DRT and log systems are quite accurate in terms of relative movement and position as regards to other ships and targets, but they are not much good for fixing your position on the planet. They can tell you how far you are from your start point and where you are relation to it now, but unless the start point was a known position, you still have no idea if you are getting close to Tokyo. (Even if you have a good fix for your datum point, error will creep in.)
To know where you are you need fixes on known positions, or a sextant, chronometer and navigation tables. No GPS in 1944, but there was radio direction finding and, I'm not sure when it came in, but the LORAN radio navigation system was operational before the war ended. As it was developed from GEE, I guess '44 or maybe late '43.

[SteamWake]

In times of bad weather it was still often possible to get a "noon sight" measuring when the sun reached its azmuth (highest point). With an accurate timepiece and knowing which hemisphere your in you can get a reasonable fix on your location.

Also dead recokoning was used, even while submerged.

Good navagators also had exteranious info such as the expeced currents, wind drift etc.

If they went for a few days with no noon sight, no star shots, yup they could be wayyyy off course.

Fourtunatly the weather being so bad you cant see the sun for three or four days in a row is pretty rare.

I suppose it could be "simulated" in the game somehow but not in its current state. You see the world of SH4 is flat. All celestial navigation is based on taking sights from a curved surface (the earth).

The sky of course is not curved however it is commonly refered to as "the celistial sphere" as it certainly appears to be a sphere.

Its amazing really that the art of celistial navigation dates back to Columbuses time. In fact their biggest obstical was an accurate time piece. The timepieces of the time relied on kinetic motion (springs, gears, and counterweights) and things like the motion of the ship and bumping the timepiece taking it in and out of its "box" etc would effect their accuracy. Even pocket watches suffered from this. Not to mention some of their tables (star logs, time logs) were at best dubious.

Using a sextant is a pretty heady subject and I dabbled in it when I used to race in offshore sailboats. Just in case the gps crapped out (which they often did) back then. Ill have to admit Ive forgotten more than I ever knew and would be hard pressed to use one now.

[heartc]

People, don't you read the forum? Check this out:

http://www.subsim.com/radioroom/showthread.php?t=113775

I was flabergasted when I read that and was wondering why this guy didn't get any responses. Maybe "Sextant Mod, Real Navigation" would have been a better title for his thread. I was about to post a few things but didn't have the time, and neither do I now.

He also posted in the SHIII mod forum about the same mod and some discussion got going. Might want to check this out, too.

[Chock]

Navigation using gyros is a lot more accurate than you might suspect, as long as you can check the drift from currents and update the gyros with an occasional celestial navigational fix or known position.

In fact, this system was used up until fairly recently in airliners when they navigated over long stretches of water, and is known as the Inertial Navigation System, it was actually the primary navigation system fitted on the supersonic Concorde airliner.

However, as has been pointed out, it's only as good as the data fed into it, and this could go disastrously wrong if the wrong data is input. Many will remember the shooting down of the Korean Air Boeing 747 in 1983 over the (then) secret base at Sakhalin Island by Soviet Interceptor aircraft. This is thought to have been caused by an incorrectly programmed INS, and was instrumental in the US President at the time (Reagan) insisting that GPS data from satellites be made more freely accessible.

These days, as a back up to GPS, 747's use an updated version of INS - IRS, or the Inertial Reference System, which uses ring laser gyros and mirrors rather than a mechanical set of gyros. It is reckoned that with the IRS system alone, a 747 can fly 7,000 miles with no further data or references, and be well within one mile of it's true position according to the instruments (and that's with having to contend with 200 mph crosswinds up at 40,000 feet and the like).

I personally would like to see the option to do celestial navigation in SH4, as I think it would add an interesting element of realism. Being able to navigate from fixes off radio stations would be cool as well - and historically accurate too - since that's exactly what the Japanese pilots did to home in on Pearl Harbor for their attack.

[starbird]

You can do that on modern aircraft as well. Just dial in your favorite AM station on the ADF, and it'll point you to it. You can also listen in.