New Astronavigation Mod (ANM) – A Conception

[silent marshal]

First the disclaimer:
Meanwhile there a a few real navigation mods for SH5and they seem to work pretty well. I for myself dont know any of them in detail because I wanted to make my own ANM. If you should find out that I solved the issue in a way which already exists, please dont’t beat me.

Now what the ANM will do:
ANM is a mod for real navigation purpose. You determine your own position by using the „Höhendifferenzmethode“, which means that you have to gauge the hight of the sun twice a day by a sextant and then you can graphically determine your exact position at the nav-map by drawing the two „Standlinien“.

General set-up:
+ the position of your u-boat is unknown (no mark on the nav-map)
+ you have to use dead reckoning
+ you have to shoot the hight of the sun twice a day
+ you need to see the sun (no bad weather) to gauge its hight
+ you can use the „Nautisches Jahrbuch“ (nautical yearbook) to read some parameters you will need for your calculation as you would do in real wordl (with porper entries for each minute of the war)
+ you can choose an easy way to find the solution (if you get rid of manual calculations)
+ your navigation officer can make all the work for you and you will get your position at the notepad (this method will even use the Höhendifferenzmethode but is more exact because the calculation is done with the exact values – no user input needed; but you have to see the sun also twice a day)
+ you can read your exakt position at the notepad if you are totally lost (GPS-function )

Lets make a testrun! Note that the shown values are all fictive, they make no sense, it’s only to show how it would work.

On the nav-map you can see the UI with the slide out bar at the right where there are buttons for manual calculation (use the sextant), automatic calculation done by the navigation officer and immediate position determination.



The green cogwheel shows you that the navigation officer had shoot one hight and is waiting for the second shot.

At the left side of the nav-map you see another pen especially for navigation markings. The mark differ from the default one because additional information ist printed on the map to help you with dead reckoning (Date, Time, speed, heading and maybe the position).



By using buttons for automatic calcualtions you will read the position at the notepad.



Now after some rainy days you will know your exact position. It is midmorning and the WO reports fine weather. Press the button for manual calculation and a new UI will appear (notice: only draft version!).



In the center you see the optics of the sextant („Halbspiegel“). With the first index at the bottom you choose the degrees, the second one is for the minutes and the third one, the „Nonius“ is for the minute’s decimals.
Before you shoot the sun (bottom of the sun touches the horizont line), you have to toggle whether you want to fill out all the white boxes or only the hight of the sun „Gem. Sonnenwinkel“: „nur Sonnenwinkel manuell eingeben“ – „EIN“.
If you decide not to use the nautical yearbook („Nautisches Jahrbuch“), toggle „Tabellenwerte automatisch berechnen“ to „EIN“, the GrW/GHA and Deklination will be computed exactly.
If all inputs are done, you can memorise the Azimut Z and the Radialversatz u.

Repeat these steps a few hours later and draw the lines on the nav-map and correct the position with the Horizontalversatz w to transform to UTM (coordinates).

After the second shot your nav-map will look like this:



The middle of the center is your estimated position („gegißte Position“) and Markierung 1 in the upper rigth sector is your exact position – pretty fun!

The accuracy depends on the precision of your shooted hight of the sun and other factors you have to read from the nautical yearbook and of course of the precision of default SH5 map tools.


How does it all work?
The idea is to determine the exact hight of the sun from the exact position (which is read from SH5 but you don’t know). Now, everytime you use the sextant, the visual hight of the sun in your optics is calibrated regardless the position of the sun of SH5. What you see is not the sun of SH5 but a dummy-sun (the right side of the optics is a fake, the left one is the true background of SH5). This will allow to use calculations as in real life.
The advantage is that this method is totally independent from the hight of the default sun and in future stages you can easily implement all the stars you wish to navigate with. For this stage the sun will be sufficient.

This is the theory so far. So, the big question is: are there some modders out there who can do all the programming stuff and help me with the UI? I have pretty no experience with this kind of modding so the realization of this mod totally depends on outer help. I am convinced that this mod would be an asset for SH5 and will make simming more interesting.

For this time it’s enough, I guess. If you have any questions I will answer with pleasure. Detailled information to how it works on demand.

Have a nice day!

[Sartoris]

I'm no modder, but I love the idea! I hope someone can help you out because I'd love to be able to use this in the game.

[Vanilla]

Accorind to my measurments the sun does not follow a real-world pattern (or any sensible pattern for that sake) on the SH5 skies, you can see it for yourself using sextant from TDW UIs mod. This invalidates the whole sky height measurement process. More to that there is a strong possibility that the sun position is dependent on the screen resolution. Even if there is a pattern, I doubt it is possible to see the horizont and the sun simultaneously given the tools we have.

[silent marshal]

@ Vanilla: you're exactly right: SH5 doesn't reflect realistic sun behaviour. The process I use is totally independent from SH5 and that's why it works absolut correctly. There must only be a script which prevents the use of the sextant-UI at heavy weather when the sun can't be seen (or at night of course) - but this for realistic gameplay only.

The crucial point of the process ist this:
If you know your exact position, you can calculate the hight of the sun. I do this as the first step (using SH5's exact position data which the player doesn't know) and now you can calibrate your sextant's scala this way that the (dummy) sun touches the horizont with the exact angle - and this for every second of a year.

See the result below: delta [Pos] ist the distance from the exact position of SH5.



I make some tests and the results are awsome. Depending on the accuracy of your input data your graphically located position is in a radius of a few hundret meters (well only if I use the exact calculation values; for real life conditions the accuracy will be 1km up and more - like it is in real world navigation).


I forgot to upload the nautical yearbook which will be written by a routine for a 1-hour period depending on your data input on the sextant-UI.



Here only the period from Minute 00-30 is shown. There will be a second page with the second half of the hour. Still in progress.

It works pretty well, belief me!

[urfisch]

very interesting stuff!

[Vanilla]

Oh, I see now! Sorry for being dumb in the first place. That's a very interesting idea!

[don1reed]

Excellent work, silent marshal. Very much looking forward to try it out.

[ETsd4]

Originally Posted by silent marshal

It works pretty well, belief me!

Sorry to say that, but that's not true.
A "graphical solution" for finding the FIXposition depends on Length/distances and arcs. The SHunter-world has different distances and different arcs. THere is a mismatch between the varying mercator-projection of the real world and the constant mercator-projection of SHunter.
The only places where SHunter and the real-world is fairly equivalent is near the equatorial region (real world= 60nm, SHunter= 64.79nm). There will be never ever a "graphical solution" you will draw with SH5 map-tools which your picture implies here ...

[silent marshal]

Originally Posted by ETsd4

Sorry to say that, but that's not true.
A "graphical solution" for finding the FIXposition depends on Length/distances and arcs. The SHunter-world has different distances and different arcs. THere is a mismatch between the varying mercator-projection of the real world and the constant mercator-projection of SHunter.
The only places where SHunter and the real-world is fairly equivalent is near the equatorial region (real world= 60nm, SHunter= 64.79nm). There will be never ever a "graphical solution" you will draw with SH5 map-tools which your picture implies here ...

Hello ETsd4!

Thank you for your critical comment. You figured out, what is the difficult part of the problem. It seems that SH5 uses some sort of UTM (Universal Transverse Mercator) coordinate system. That means, that the higer to the north or south you are, the mote distances (width only) are streched. You can check this when you compare distances from SH5 with the ones in google earth. (I know, you are firm with all this, but maybe there are some readers who aren't.) For simming this means that you are travelling a greater distance as you would do in real world.

I have factored in this fact and that's what the "Horizontalversatz" is doing: it corrects the sphere/plane geometry of the "Höhendifferenzmethode" to the UTM system.

How my method works:
The calculation bases on a spherical system. Because of the great distances, we can transform it to a plane system, where circles are lines - that's what you are doeing in real world also. I can do this at the nav-map but consider not the coordinates of default SH5. Now I have to transfer the intersection point - which is the exact position at the sphere - to UTM of SH5 and this is done with the "Horizontalversatz".

I will make some more tests but I wonder if there are any errors left.

Critical comments always welcome! If I am wrong, ashes to my head and I will submerge into the deep of www. If I am right, SH5 will be more exciting.

[don1reed]

Both SH3 and SH4 have MapFiles. In SH3 it's located:

C:/Documents/SH3/data/cfg/Careers/skipper's name/0/_____.Map

In SH4 it's located:

C:/Documents/SH4/date/cfg/SaveGames/00000000/SaveData.Map

There isn't a "Map File" for SH5. (That I know of.)

An amateur mathematician, Celestial Navigation Enthusiast and practicianer; not to mention, an all-around nice guy, Michael Jones, created a script file using Python and Stellarium to take the data from the SH4 Map file and convert the numbers found therein into Geo Coords. Numbers such as:
-1198199.13, 6006413.50,0.00

by dividing these numbers by 120000.

i.e., -1198199.13 / 120000 = -9.9848993. The (-) sign indicates West Longitude and South Latitude. The quocient then becomes: 9°59.1'W.

6006413.50 / 120000 = 50°3.21'N.

Everytime a "save" is done on your computer while playing, it auto-updates your true position on the game chart, even if your boat's icon is hidden.

Alas, SH5 does not have a MAP file that I know of.

And, of course, the Python/Stellarium method of celnav was used because the celestial canopies in SH3 and SH4 are not accurate, whereas, Stellarium's canopy is true.

Once Python obtained your true coordinates, it pulls up Stellarium and presents the correct celestial canopy you would be viewing if you were in fact, at that location. All that was left to do was to take of round of virtual sights of altitude and azimuths of selected bodies and have Nories, or HO Pubs 211, or 229, or 249 and almanac at hand to do the sight-reduction...five times per day, as in real life.

Then again, the next problem was the matter of the Mercator Projection Chart. None are true in the SH games. They're charts meant to fit the resolution of your display. So...forget Dead Reckoning as well.

When Navigators purchase charts from authorized chandlers, the charts they buy are printed to very precise specification and are miniature ratios of the real world, i.e., 1:1,000,000 scale. This is an extremely precise ratio, which means it is accurate to the length of one Toyota Prius to 1M Prius, or 1 nm to 1M nm, or 1cm to 1M cm, etc. One could say it's etched in stone. The chart in these games...not so much.

Edit: I'm looking forward to see this come about and wish you great success.

Cheers,

[HerrFritz]

Very interesting idea , sir! I'm waiting such a mod for years.May I ask you where from is that sextant interface and if is it functional ? I would like very much to try it.

[reaper7]

Outstanding. PM sent .

[TheDarkWraith]

how are you making this pen add information to the nav map? And how are you getting this information (pen mark and additional info) to scroll with the nav map

[silent marshal]

Originally Posted by TheDarkWraith

how are you making this pen add information to the nav map? And how are you getting this information (pen mark and additional info) to scroll with the nav map

This is exactly the problem: I don't know how. I have reflected what I would need and made some postworks with photoshop. To breathe life into these ideas I depend on experienced modders/programmers.

The calculation background is ready, now I am waiting to launch the next phase.

I assume that SH5 always knows the exact position of the boat. This is the most important information I need. The rest ist pure calculation.