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.

[tonschk]

Indeed very intresting

[quink99]

As one who has done a bit of RW celestial navigation in both sailboats and aircraft this would be the ultimate in immersion, challenge, and fun.

My congratulations, Silent Marshal! It won't be easy but it will be worth the effort. Good luck!

[LemonA]

The mod should do this:
the more rolling of the boat in the swell the harder to get an accurate "reading" from the sextant.
Real sailors take 3 or more Sextant-shots at one session to minimize human errors and control their sextant-readings.

But i see in your concept this:
exact position = just bringing down the lower limb of the sun until it intersects with the horizon at two different times
+ doing some mathematical drawings


Actual what you see through a sextant for example at quit swell is more like this...




The GUI looks excellent.


What do you do here exactly?

Links for the "Höhendifferenzmethode"-method?


I would prefer a complete nautical almanac (pdf-book) instead of computer generated mini-tables for my current position.


Are you plan to calculate the arcdifference horizon <-> lowerlimb of sun at your own? Formulas? Example?

[silent marshal]

ROLLING OF THE BOAT:
The human errors are an important point: they mostly determine the accuracy of our calculated position. I am not sure how to consider the rolling of the boat because in the sextant GUI the left side of the mirror is the "real" background (comparable with the UZO view: up-down-up-down...) but the right side is only a picture which is moved along the vertical axes. I don't know how to deal with this issue. I for myself would be satisfied if it is possible to make the horizont steady, regardless the rolling of the boat.

BACKGROUND OF THE METHOD:
A good source to understand what the "Höhendifferenzmethode" is about: www.kowoma.de/gps/astronav/allg_methode_1.htm (german page). There you can also find some hints about the graphical solution. I will explain some special corrections for use with SH5 later on.

ALMANAC:
The problem with the complete almanac is that you have to consider every minute of a year. This is possible to do but a lot of work. The point is, you have to find your day, the hour and minute and then read the data you need for your calculations. So you have to dial these inputs correctly to avoid false user input (human error). With the dials at the GUI, this human error factor is factored in.
But it's possible to make a complete almanac for the years of war.

FORMULAS:
All values are calculated with formulas (hight of the sun etc.). This is essential to get the azimut (A) and the Radialversatz (u); without them you can't determine your position. Examples of the formulas will follow soon (it's a lot of stuff).

ACTUAL TASK:
At the moment I am working for the method how to factor in the moving of the boat from T=1 (first shot) to T=2 (second shot), which will be used more often. Some more mathematics to do...

PS: I implemented only my sextant-buttons to the GUI of Dr.Jones. Hope it't ok for you, Dr. Jones...

Bravo Marshal!!! To which interface will this mod??? Thanks for the reply!

[THE_MASK]

You can have a steady horizon looking thru the uzo by ticking the in game difficulty setting .

[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 .