Real Navigation Mod

Great but while playing in 1680x1050 the dashed map outline is ... softened (gradient) so it not even near precise anyhow.

Verdammt...

I'll give a look if it's possible to turn off going off course in schwere wesser.

[divingbluefrog]

It should be.... but I'm still investigating this field and I'm in the fog....an heavy one....

But I've good hope that someone will find the solution. Weather does not alter the course when playing assisted mode. Now we do exactly the same thing, give an initial heading and let her go....
A waypoint, in a way or another, force the sub to go exactly on it, but we know now that the wind's speed and direction influence the course, it means that the program make constant correction of the bearing.
It's not a matter of variating speed, if so, we should keep the bearing, but have a error on the ETA. In assisted mode, the ETA changes when the weather changes.
I'm just beginning a new set of tests and I hope that I will have a clearer sight at the end....

[divingbluefrog]

Hum, I have a good and a bad news.
The good one is that the drift problem in heavy weather is solved, the bad one is that there is no problem.
I suspected the truth since the beginning but lack of a truthfully compass I couldn't verify it. Now it's done. Our Elite helmsman do their job and they do it well. Drift in heavy weather is a reality, as anyone with a sailing experience could tell you. And the model provided in the game is more or less accurate, rather more than less IIRC my past experiences at sea.
I will not give all the details about the tests I made, but to sum up :
- your average speed rise when the wind blows from behind and vice versa, in respect to the lost of speed due to the surging sea.
- you drift in the direction of the wind, and the drift is proportional to the wind speed.
We wanted realism in the sim, we get it...
The dev made only one little error which will save our lives. The compass give you your true heading, not the initial one. Of, course, you aren't obliged to read your compass after a long ride in rough water...
For the speed variation, no other means that your best estimation.

Good hunt, fellow Kaleuns.

Originally Posted by divingbluefrog

The dev made only one little error which will save our lives. The compass give you your true heading, not the initial one. Of, course, you aren't obliged to read your compass after a long ride in rough water...
For the speed variation, no other means that your best estimation.

Yeah the sim might be correct but still we need constant adjustment to our course. For me it should be that way. Helmsman corrects all the time to keep us on 0° course and after 500km we end up still heading 0° but we're 20km SW from our estimated end point because of drift, wind slowing us down etc.

In a very heavy weather I let them go, hit the TC and watched. We end up heading 60° of given course... probably we would be doing circles soon...

[divingbluefrog]

It's not really surprising... Imagine that, you are caught in a storm, not the most terrific one, but a serious, wind speed 15m/s which is equal to a 10 in Beaufort scale, with a surg of 7-8 m. And you have to keep the course on, say, 0°... but the wind is blowing straight port, and so is the surg direction. The ship will easily show a helms compass moving from 355 to 05, and you will try to keep it in the average position.
Your speed is slow, 7-8 Knts, with sudden acceleration and short braking when the fore hit the wave, the ship isn't really well responding to the helms.

This is modeled in the game by a 1-2° drift per hour for an average distance of 31-32 km, which seems very close to the reallity. I don't think that high TC (I mean 256<, never play above) have any influence on that. But for sure if you let her go for 15 or 20 hours in a raw whitout giving any corrections, you can easily be out of course for 30-40°.

Major rule for the RealNav navigator : in a storm, stay on the bridge, or you will get lost.

[ichso]

The thing is that noone says the subs behaviour under stormy conditions is unrealistic. It's just tiring to play sometimes if you have to click on the compass every 2 seconds under 128x TC.
Imagine that if you want to travel over to NY and the storm wouldn't end for 1-2 weeks.

That's where it isn't fun to play anymore so we would like to give the task of keeping course trustfully in the hands of our helmsmen

[divingbluefrog]

But you can as the compass give you your true heading. It's just a matter to make one correction point every day.
If you travel to NY, roughly, you will get a 270° heading. After the first day of storm, you find a 260° heading. Well, you spot your new estimated position. You set a new course to, say, 280°. 24H later you find a 282° true heading. New correction and so on.

[ichso]

I know that the compass gives the correct absolute heading of your sub. But the matter cannot be solved that easily by correcting the course once a day because of the thing that Hadrys said sometimes he got off course by 60° (I assume he meant in far less than a day).
Also if you correct an error of 10° in your course by 10° in the opposite direction you want to travel you produce even more error because the course changes slightly over time and not abrupt all at once. But I don't know how big this error would be in the last case this might be the smallest problem overall.

Originally Posted by ichso

I know that the compass gives the correct absolute heading of your sub. But the matter cannot be solved that easily by correcting the course once a day because of the thing that Hadrys said sometimes he got off course by 60° (I assume he meant in far less than a day).
Also if you correct an error of 10° in your course by 10° in the opposite direction you want to travel you produce even more error because the course changes slightly over time and not abrupt all at once. But I don't know how big this error would be in the last case this might be the smallest problem overall.

It was a f..in storm of the year, I've hit TCx256 and watched how the compass turns on my eyes like in roulette...

Problems produce problems. If we assume a correction once a day that would be: we are +10 so for the next day go -20. But under condition that speed, sea state etc are the same. So the only way to navigate properly in heavy weather is to constantly click the compass. I can see that when allowing up to 3-5° divergence in 128 (256max) and than clicking -3-5° should give a nice accuracy but this is insane when you need to go 5000km even in a straight line!!! Add up to this plane attacks after max 2hrs on the surface (maybe 4 during night above 60°N which isn't that dark...).

[ichso]

I really don't know in which RealNav thread to write, there are at least 3 big ones of them.

I have a little suggestion as I made a little mistake while playing yesterday:
I accidently deleted all my drawings on the nav map with the stupid delete-all button (which doesn't even ask if you REALLY want to erase EVERYTHING ).

In the ...\data\Menu\*_menu.txt files are the functions of these buttons listed, I commented out the ones which refer to the everything-eraser. To be sure I did that in the de_menu.txt and the en_menu.txt although just the de_... should be used in my case.

Didn't test it yet, will do it later.

Did you erase your entirecourse plottings from weeks of patrolling accidently ? This is really frustrating. I don't want to redraw it from my written log book either.

I'm also a little confused by the three RealNav threads. I'm trying to get my head around Real Navigation, even bought a book on Astronomy to try and figure it all out but it's a tad confusing to say the least.

Could someone list the basic steps required to determine my boats position ? I can then trawl through stuff in these thread and online to put together a detailed process of steps to use in SH3.

I don't think we can expect people to play only in real time and clicking the compas dial every couple of secs in storms is also a pain so perhapps we should just accept that storms will throw out our calcs, at least until there's a break in the sky to get a decent celestial fix and then make compensating course changes. Would this work ?

I'm thinking of Worsley's epic navigational feat in the James Caird with Shacklton and Crean between Elephant Island and Prince Hakkon Bay, South Georgia. Worsley could only make a couple of sun shots during this 800mile crossing yet still managed to find South Georgia, an Island which is effectively a needle in a haystack in the South Atlantic.

Surely it must be possible to successfully navigate our boats with the Sextant mod, some tables and course compensation ?

I admit I may be over simplifying things as I'm still TRYING to get my head around all this, having never learnt navigation prior to following these RealNav threads.

Thanks....

[ichso]

Ok.
The description from the manual of how to use the sextant is pretty useable. The manual that came with the mod.

When at the northern hemisphere wait for something around midnight, this can make finding Polaris a bit easier.

The sextant is best used from the f10-deck gun view as this is much better stabilized than the brigde view.

Align the sextant scale with the bottom and top of your screen as it is shown on the screenshots in the manual or somewhere early in this thread.
Then just take the reading of Polaris' height above the horizon.

If you are new to this mod you should first attempt to get your latitude by this method and then compare it to your real postition.
For me it worked very well to use the course plotting tool. With
RealNavMod installed this wouldn't let me actually plot a course but shows me my exact position.
By cheating this knowledge you can get more used to the mod.

Measuring longitudes is simply a matter of measuring the time difference between your local time and GMT. GMT is the time displayed in the rightmost down corner of the screen, with the white background.

Getting the local time is done by waiting for the sunrise and comparing that time's difference to the value of Van's SR/SS almanac that came with the mod too.

Let's say you measured your latitude to be 54°N ad midnight. You kept this latitude by travelling 270° or 90°.
New you look in the almanac and search there for the table containg your specific time of the year.
From there you note down 2 values: the sunrise time for 50°N and the one for 60°N.

For example you're in Feb. 15th, the almanac states that SR time for 50°N is 7:12 a.m. and for 60°N it is 7:40 a.m.
Now you know that you are 4/10th between 50°N and 60°N (assumed above).
So you interpolate the SR time for 54°N, this would be:
0.4 * |7:40 - 7:12| + 7:12 = ~7:23 a.m.
This time you note down.

Now you wait for the sun to rise. We experienced that the most exact moment (in terms of this game) is the moment when the redlight gets turned off.
Exactly at this moment you write down the GMT shown in the right down corner.

Now you know that your local time is 7:23 because that's the SR time for your 54°N latitude and you can calculate the difference to GMT.

Let's say your GMT clock showed 8:35 when the redlight got turned off. This means you are 1:12 behind GMT. Every 15° longitude (west or east) mean one hour time difference. So by 1:12 hours (behind GMT) you get a longitude of:
12/60 = 0.2 => 1:12 = 1.2h => 1.2*15 = 18°W longitude.

Hope that wasn't confusing at all

@ichso

Hope that wasn't confusing at all

Confusing?!!! My god man that's the most clearest explanation i've read on the entire subject!!!! Thankyou immensely.

I was getting there but started getting confused by some of the posts regarding the second clock above the GMT clock. Some say its local time but gets screwed passing GMT and some say it updates half way between longitudes. I say...HELP!

Just a couple more questions if possible:

1) Is it possible to get lattitude readings by sun spotting using the sextant ? If so then a combination of both Sun and Polaris spotting should increase my position fix accuracy.

3) I should be able to fairly accurately track my course between fixes using distance = speed * time ?

2) In fine weather and calm sea states i should be able to navigate away from a known lattitude (other than heading 90 or 270) before knowing my longitude and still obtain a fix on my position by doing the maths ?

4) In rough sea states I should expect to end up off my intended course due to drift. The ammount proportional to the duration and severity of the rough weather ?

5) If SH3 allows sun spotting then I should be able to correct my position fix by shooting the sun in cloud breaks during a storm...if any ?

6) Is it really necessary to force the helmsman to maintain course during storms and high time compression by constantly clicking on the compass ?

7) What is the max time compression i can use in order to stay within a healthy margin of positional error and why ? (I have also read that the clock goes a bit wobbly during high TC).

Thats it, and once again I really do thankyou for taking the time to answer these probably very obvious questions

[ichso]

This is only obvious if you already know the answers

As you ask this sun-shooting with the sextant I get interested in this again, didn't manage to do this right yet either. But I just learned on wikipedia that many captains got blind on one eye by looking into the sun with a sextant

It should work if the sun is at it's zenith, that would also give away your current longitude as you know your local time would be 12:00 at this moment.
But I don't know any practical way to see if the sun is at it's highest point in SH3.
Perhaps wait til nearly noon and then just stare into the sun for a while under 32x TC ? :hmm: Have to try that.
And hopefully won't have to wear an (no, not a hat) after that.

I should be able to fairly accurately track my course between fixes using distance = speed * time ?

Just a little hint, I even don't use myself very often:
The line drawing function gives away slightly wrong values as which the current drawn line is.
More precise is the combination of the scale of the map and the use of MooseMeasure:
http://cip.uni-trier.de/~schmidt/sh3/LineExt.tga
(goes to ...\data\Menu\MouseCurs\)
(a precise plotting tool, don't be shocked about it's visual size though )

You can of course plot your course really precise, especially if you do it with minute-precision. I think I've got too lazy to do it THAT exactly though and it still works out in the end.

If you got in some attack at an convoy or get chased by DD's you won't know your exact position afterwards anyway.

6) Is it really necessary to force the helmsman to maintain course during storms and high time compression by constantly clicking on the compass ?

7) What is the max time compression i can use in order to stay within a healthy margin of positional error and why ? (I have also read that the clock goes a bit wobbly during high TC).

This is still odd. We found no way to make the helmsman keep exact course yet so it's still clicking the compass like crazy under higher TC and in bad weather conditions.

The error in the set course seems to be not that easily predictable either. It's not to be calculated out of wind speed and direction + own course. That's too bad.

Also, sometimes I felt like going under 512x didn't produce a drift as high as when using 128x or 256x. But some other times it really didn't matter.

You can even course errors out by 'over-correcting' it when it got wrong, it's a matter of experience though.

And in the end it's not even that bad or unrealistic to be some few degrees off course. At least you don't just spawn here, race there, this was a bit too easy in the long run

Excellent posts, pretty much sum up the state of play re Real Navigation....and thanks for the Moose Measure, I quite like it to be honest. I've had my fun being a captain, so now I want to try my hand at the being the navigator. I also imagine shadowing targeting convoy's via Hitman's research will add to this.

I don't mind being a little uncertain of my position, uncertainty is good and realistic, just wanted to make sure I wouldn't be really off course.

I'll start putting all this into practice over the weekend....thanks mate