RealNav navigation..

[don1reed]

Howdy Vanjast.

I'm snuggling up to 70yo and have been using Celestial Nav via sextant before the USN quit teaching it at Annapolis; however, when I saw your post re RelNav...I took the bait and had to give it a try.

Some of us have been scratching our beans trying to adapt CN into this Sim since it first appeared on the market. We always came up short as we discovered the celestial canopy was close to real (eye candy) for the war years, but no cigar...if you know what I mean.

I'm running a patl just west of England at 53° 40'N, 001° 25'E.
Time: 16:00 GMT...see below. I'm using your mod and as you can see, the sextant reading is about 9° off from "Navigator's" starfinder, or somewhere out in the middle of the Atlantic (540nm).

If I'm doing something wrong...please correct me, or if I'm using the sextant at the wrong times..please let me know.

At sea the sextant was used at dawn (morning round of stars), again around 0900 to get a running fix, Noon sight & fix (for etmal), about 1600 to get another running fix, and finally at evening twilight fix with round of stars. (unless wx was overcast).

Please post how to successfully use your mod.

Tnx,

[poor sailor]

Originally Posted by don1reed

Please post how to successfully use your mod.

You may look at this guide by vanjast http://www.vanjast.com/NavMod/QuickNavGuide.pdf

[don1reed]

Tnx for the response, Poor Sailor.

Are you telling me of all the 52 navigational stars, Sun, Moon, & 4 major navigational planets--that using this mod we can only navigate using the pole star, Polaris?

Right. Ok. Just so I know.

I've been getting frustrated and have been frustrated since Mar 2005 trying to virtually navigate using celestial bodies mentioned above using several real world navigational programs, so I abandoned the idea long ago.

If, polaris, is all that works, then I guess it'll have to do. I originally gave up on using the pole-star due to it's high altitude while operating in the North Sea, (it was usually just too high up for my screen to be able to capture, both the body and the horizon simultaneously.)

Tnx agn.

[vanjast]

Hi Don1Reed, sorry for the delayed reply..
with regard to the Sextant, it currently works on the game default resolution of 1024x768. I've tried a 1280x1024 image but still have to sort out problems here.

(See image below) When taking a reading one has to horizontally rotate your screen view until the star is close to horizontal(X-Axis) screen centre. I had to do this as the vertical angle of the star changes with view rotation along the X-axis. the screen centre is the best(only viable) reference point in the game.

Next the sextant image is dragged out and placed left-off centre of the screen, with the top and bottom alignment markers just off screen.

After this you vertically rotate your view until the bottom of the screen aligns with the horizon. This has to be done as the game vertical screen scale is non-linear and the horizon is now the next reference point. You can now take a reading.

Also from what I've experienced so far The stars and constellations are in their correct positions with repect to time, so any star reading can be taken. Some body else here has already triangulated their position to 10nm accuracy so it's looking good so far.


The next image gives a visual idea of what is done above Plus the part that you were concerned about - angles above 60 degrees. The default game screen gives a vertical view angle of 60 Degrees, so if you want to 'shoot' 60-90 degrees one has to vertically rotate the scrren view to it's max.
This places the centre point of your screen at 90 degrees directly above you with +- 30 degree views either side of the vertical. I've found the scale here to be consistent with the horizontal view. You will now have the 60-90 degree view angles


Once I've sorted out all the different screen resolutions, I'll put a proper document together, as it is a bit lacking at the moment.

Thanks
Van-o

[Georg_Unterberg]

Hi don1reed,

it's strange: I get a good result at this position and time:
Your almanac states 20°21' for sun elevation at 10.Sep.1939 - 1600 GMT - 53°40N - 1°25E
I copy that, got same result with my almanac. Using SH3 to make a mission at that time & position I warp to the eastern coast of England and shoot the sun at about 20° (center) - which is ok!

Please check:
- date and time in SH3 correct? You calculated for 10.September 1939 (09/10/1939)!
- position in SH3 correct? You said you are west of England, but your position is in fact east of England!

hope i could help you

cheers

Originally Posted by don1reed

Howdy Vanjast.

I'm snuggling up to 70yo and have been using Celestial Nav via sextant before the USN quit teaching it at Annapolis; however, when I saw your post re RelNav...I took the bait and had to give it a try.

Some of us have been scratching our beans trying to adapt CN into this Sim since it first appeared on the market. We always came up short as we discovered the celestial canopy was close to real (eye candy) for the war years, but no cigar...if you know what I mean.

I'm running a patl just west of England at 53° 40'N, 001° 25'E.
Time: 16:00 GMT...see below. I'm using your mod and as you can see, the sextant reading is about 9° off from "Navigator's" starfinder, or somewhere out in the middle of the Atlantic (540nm).

If I'm doing something wrong...please correct me, or if I'm using the sextant at the wrong times..please let me know.

At sea the sextant was used at dawn (morning round of stars), again around 0900 to get a running fix, Noon sight & fix (for etmal), about 1600 to get another running fix, and finally at evening twilight fix with round of stars. (unless wx was overcast).

Please post how to successfully use your mod.

Tnx,

[don1reed]

woops...typo. Meant East of England. tnx Georg.

And tnx, van, for the explanation. I'll have to fumble around with it abit to get my sea-legs adjusted.

-...-

Georg, the date & time is correct as my pic shows; however, my Windows/print screen function peeled away some of the sun-glare and shows the Sun's position in the middle of the screen (roughly) where I believe, van, is referring with his pic. As you can see, the "Navigator's Star Finder" shows Hc for the Sun as 20° 21.0'. The closest I could get to that was about 29°...also show on my pic. 9° off (540nm) is not too good.

The non-linearity of the screen is (no pun intended) throwing me a curve.

[Georg_Unterberg]

hi don1reed,

if you hover with your mouse over the "ship time" 16:00 in lower right screen you get an additional local time reading - does the local time also show 16:00?

edit (my theory):
i could bet it shows you 17:00, an indicator that you started the mission in timezone +1.
So if local time and ship time is different, the ship time reading (16:00) is NOT the real GMT. To get the real GMT for your almanac prog please subtract the time difference (local - ship time) from the displayed ship time.

In your example: (1700 local - 1600 ship) = +1h. GMT = 1600 - (+1h) = 1500

In your picture in SH3 you are seeing the sun at 15:00 GMT.


edit again:
Just saw your answer below. I refrain from my theory. I'll check this later...

Originally Posted by don1reed

woops...typo. Meant East of England. tnx Georg.

And tnx, van, for the explanation. I'll have to fumble around with it abit to get my sea-legs adjusted.

-...-

Georg, the date & time is correct as my pic shows; however, my Windows/print screen function peeled away some of the sun-glare and shows the Sun's position in the middle of the screen (roughly) where I believe, van, is referring with his pic. As you can see, the "Navigator's Star Finder" shows Hc for the Sun as 20° 21.0'. The closest I could get to that was about 29°...also show on my pic. 9° off (540nm) is not too good.

The non-linearity of the screen is (no pun intended) throwing me a curve.

[don1reed]

Georg, I'm in the Greenwich time zone.

Here's another example:



As you can see, we have the constellation Orion in the center of the screen.

Betelgeuse is 3° off
Bellatrix is 11.6° off
Rigel is 9.5° off
and over to the left a bit is
Procyon and its off by 14.75°

(Compiled a RW sight reduction on those number, btw, and it would put me 63° 58'N, 000° 19.8'W.) 634.7nm by great circle calc.from my actual fix.

So, I'm at a loss...except for cntl-left mouse. :hmm:

[vanjast]

Don1Reed :- Sorry but you are placing the sextant in the wrong (vertical) position.
Have a look at the image sequence below.

You are placing the bottom of the sextant on the sea horizon


Whereas you must place it so that it exactly fits on the screen (1024x768 resolution). On a bigger screen AFAIK you must fix it on the bottom of the screen


You then pan your screen view vertically until the horizon is on the bottom of your screen. Here I've lowered it a bit so that you can see the horizon/sea


When this alignment is done then can you take a reading.
Hope this makes it better

[vanjast]

Originally Posted by don1reed

So, I'm at a loss...except for cntl-left mouse. :hmm:

Remember that this is not a GPS nav system (like ctl-LMouse) so navigation is not
that accurate.
With this mod, I think it will be accurate to say that that this is the 'technology' that they had to deal with - sextant and tables. So there are going to be in accuracies in navigation.

I've limited my time acceleration to 256x and kept strict notes on times, speed, course, etc.. and found myself to be within 5nm after a 5 day blizzard. OK we don't have to take currents into acount, but it's only a game and a good education (for me) non-the-less

Having said that I found great enjoyment to pin-point my exact position after many days of overcast skies, rain, sleet and snow.

I'm getting soppy now
Must refill my glass

[kevtherev]

Originally Posted by Georg_Unterberg

ok, I got rid of the tail - it's the file data/Menu/Gui/ContLine.tga (thanks to Rubini for finding out everything about this file)
If making it transparent, all the tails are gone. BTW I use GWX 1.03. In NYGM 2.5 the modders may have eliminated the tail right away.
no need to look into it further, problem solved

Great news Georg, I am using Paint Shop but cannot seem to make the ContLine.tga transparent, no matter what I try there is still the 'tail' on my map. Can you give me a quick know how on this procedure ?
PS: I have only tried to 'dissapear' my own sub indication, I have not done any furthet installations, except the UnitSub, UnitSubM and UnitSubL replacements with the ones from RealNav mod.

[don1reed]

Ah...........hah!

(A Eureka moment)

I was using the bloody instrument incorrectly :rotfl:

With every circle of equal altitude....one never knows.


Later,

[Georg_Unterberg]

hi kevtherev,

I used GIMP to edit the contline.tga. I found out that to remove the tail its not necessary to delete the whole line - which is 256 pixel long. By using the eraser (rubber) tool simply delete the leftmost 50 pixel and the rightmost 50 pixel of the line and save as uncompressed .tga.

I can upload my contline.tga, but its only for GWX 1.03 - should I upload it?

Originally Posted by kevtherev

Great news Georg, I am using Paint Shop but cannot seem to make the ContLine.tga transparent, no matter what I try there is still the 'tail' on my map. Can you give me a quick know how on this procedure ?
PS: I have only tried to 'dissapear' my own sub indication, I have not done any furthet installations, except the UnitSub, UnitSubM and UnitSubL replacements with the ones from RealNav mod.

[heartc]

Vanjast, I just want to thank you for this great mod. I'm not yet using it as I've yet to learn the basics, but I know I eventually will do so and enjoy the heck out of it. I remember quite some time ago there was a thread discussing the possibility of "real life" navigation by shooting the stars / the moon / the sun in the game, and back then the consensus was that it can't be done (something about that the world in SHIII is flat). But seems like you found a way and even if it would still be limited to some extend by the game setup, it seems to be accurate enough.

I remember another problem though which was discussed then: The fact that the rudder (or the "helmsman") would not compensate for sea currents to stay the course when you enter the heading manually, other than when the course is plotted on the map. That would result in an ever increasing error, drifting you off course, and require constant position checks.
What is your experience with that?

[don1reed]

I have to admit, van, that it was "force of habit" to use the horizon as my base...because thats what I do with real sextant. Sorry for the confusion.

Accuracy at sea is a relative thing. Kriegsmarine grid squares were 6nm x 6nm (at their smallest). Anyone on the tower could see anything within those squares, at least "smoke on the horizon" for sure.

When the Naval Academy taught Cel Nav, their standard was accuaracy to within 0.5nm. (1000yds).

Cheers,