Real Navigation and the sextant

[Kelly621]

I have been using TDW's real navigation and Trevally' navigation script and really like the new facet it adds to SH 5. I was wondering about the Sextant tool...is it usable? Can I use it to get my fixes instead of the Nav doing it for me?

I picked up a bit on dead reckoning navigation and rules of the road (bouy's) years back when I use to go up to control and hang out with a good friend who was a Quartermaster. He taught me quite a bit on those slow and quiet mid-watches., but I really never learned much about the sextant or how to use it. We had one, but it was not used much on the sub:)

Kelly621

Never mind...found what I needed in TDW real nav readme...sorry for wasting space on the forum

[Bothersome]

Pretty much the sextant can be used to find the azmouth (?) of stars, the Moon, or Sun. But I tend not to use it because you'd need star charts and other complicated documents to make use of it.

Dead Reckoning, is a bit too far off for what would really be done. I do a much better job of calculating my location via heading, time and speed. Using the Nav officer for a second opinion on celestial helps sometimes but most times I'm way more accurate than what's programmed into the game.

My guess is that the game knows your exact location but when asked, it puts a random figure into it to make it off some, instead of best guessing.

Especially, DR has too much course deviation. 90 degrees west is pretty damn close to 90 degrees west. 18 knots is pretty damn close to 18 knots, so travel for 10 hours west is not going to be off by 5 degrees and not away from target by more then a few kilometers. But DR can be off by way more than that. Like some first grade schooler done the figuring.

All in all, more ppl should try the real navigation mod by TW, because it's not near as scary as it might seem. I didn't try it for so long because I could just imagine what would be necessary to get back to port (or to even find it). But surprisingly, it's pretty easy to figure out how to know about where you are. And close enough is usually good enough. More importantly, it helps add depth to the problem of finding and tracking that convoy. Like, "Am I going in the right direction to intercept?, Do I need more speed or less? How far away is the convoy? Will they hear me? Is this damn fog gonna ever lift?"

[Kelly621]

Bothersome,

I am just messing around with the sextant now....interesting, but I will stick with the same method you are using. I watched Stoainm's real nav video which pushed me toward that method. And your right it is more accurate then the DR function.

My guess is that the game knows your exact location but when asked, it puts a random figure into it to make it off some, instead of best guessing.

Agree....sea currents and heavy seas and wind when you are on the surface affect the accuracy of DR. We were running out of Japan years back, on a fast attack, on the surface in heavy seas and wind heading out to our dive point. The helmsman had his hands full trying to stay on course. If we had been using DR it would have been no better than a guess. I doubt if SH 5 models these factors in.

Real navigation is not everyone's cup of tea, but I think a number of members here are using it.

Kelly621

[Fifi]

One thing wich isn't modeled ingame, is the sea stream...
Very important for real nav calculations!
Other thing: boat speed may vary in regard of waves and wind.
Not modeled too AFAIK.

But game is enough hard like that :D

I would really want to know how to use SH5 sextan without officer help though.

[Kelly621]

Fifi,
Read through TDW's information he provides with his Real Nav mod. He talks about using it within the game. I am still messing around with it out of interest, Agree,the game is complex enough with all the mods added in. Had enough ultimate reality of submarines in a 24 year career.....kind of like my game toned down a bit from that :)

A quick more concise answer....read the file named "using the game mod" in the Real Navigation document folder....he gives an example of using the sextant.
Kelly621

[Fifi]

Thanks Kelly, will have a look into it :up:

[THE_MASK]

http://www.subsim.com/radioroom/showpost.php?p=1567721&postcount=35

[Kelly621]

Sober thanks for that bit of info....are you using the sextant? ....if so what does it add to the game for you? Just curious :06:

[THE_MASK]

Sober thanks for that bit of info....are you using the sextant? ....if so what does it add to the game for you? Just curious :06:No i dont but some people probably do .

[gap]

I haven't ever tried using the sextant, but I have read somewhere that SH5's celestial sphere is not very accurate :-?

[volodya61]

@Kelly621

Have a look at this thread - www.subsim.com/radioroom/showthread.php?t=194033 (http://www.subsim.com/radioroom/showthread.php?t=194033)

[Kelly621]

Volodya61......thanks, an interesting read.

[Gauthier]

Hello,

did anybody succeed to use sextant, clock and tables to get himself a complete fix?
I never saw a complete example.
Even in the readme files and docs included in the mod.

Tks
G

PS By the way, can someone explain how to activate the sextant in the GUI, because for now, I have a sort of stadi displayed that doesn't seems to function...

[oakdesign]

Sjizzle already did calculating a fix using the new sextant included in the TDW 7_5_0 version wich is only released as a test version at the moment.

The this post where he shows a screen of his nav map drawing for a night fix.

http://www.subsim.com/radioroom/showpost.php?p=2091025&postcount=10609

In another thread he stated that he might make a sextant tutorial soon
http://www.subsim.com/radioroom/showthread.php?t=206103

Another thread you might be interested in is a WIP in progress by myself. Bringing more information onto the navmap. As a begin I started with adding all the nav buoys at their postition on the map
http://www.subsim.com/radioroom/showthread.php?t=206373

[Sjizzle]

I haven't ever tried using the sextant, but I have read somewhere that SH5's celestial sphere is not very accurate :-?

it is very accurate .... i will make some screens and will pos here :)

EDIT:
here we go the screens

http://www.mediafire.com/convkey/b8f3/k7w0hgx0au5ytuffg.jpg

http://www.mediafire.com/convkey/c300/zrn3laiv6mzf7difg.jpg

[Gauthier]

Thank you very much for the help.
I'll wait this tutorial for celestial lop.

But afaik, my "sextant-stadi" can't measure more than a 16 deg angle or so.
Maybe he did with the lower stars?
Or is it possible to go higher?
Tks a lot.

[Gauthier]

I didn't see screenshots... I'm glad to see you are on the way...

[Sjizzle]

Yup can't measure higher then
16 degree u must use some lower stars ... Capella some stars from big deeper etc
Polaris its to high..
And what is sad star almanac are not free ...there are
Some internet page with star almanac
my tutorial is almost done

[Gauthier]

Couldn't we use a mask in the obs that can point up sky? Or older version of sextant (red lines across full screen) (that I can't activate now)?

I'm in a hurry to try your tutorial...
Thank you.
G

[vdr1981]

Ahhh, celestial navigation...My ultimate goal in SH series...:D To sail from Kiel to France (or even further :hmm2:) without any help. Cant wait for your tutorials Sjizzle,tnx!

[Sjizzle]

Couldn't we use a mask in the obs that can point up sky? Or older version of sextant (red lines across full screen) (that I can't activate now)?

I'm in a hurry to try your tutorial...
Thank you.
G

the old sextan from TDW_UI's 742 work great u can mesure all stars ...

[Mudraxus]

Hello Kameraden!

I downloaded the TDW mods, including Real nav a couple of days ago, and did quite some research on Nautical navigation. But I ran into two Problems.

Following Situation. I'm enroute from Helgoland to Scapa Flow. I have a rather accurate DR Fix (done by myself) and find myself around 55°48N' 3°46'E . One would expect that the sunset and rise is round about 16 minutes earlier on the GMT Clock than it's stated in the Almanach Table or the Shift-B Board. But the SH5 Reality is, that these events are happening over an hour after the times, putting me in the Atlantic instead of the North sea.

Second Problem, shooting Stars with the Sextant (The Red Vertical thingy) . I have a Free Sextant Calculation App for my android Phone, so I punched in three Stars, (Polaris, Mirach and Dubhe) and the App told me I was over 1000 nm SW of my Current Posit. At the same Time I was looking up the exact situation at Stellarium and I figured out that there seem to be Errors between 12 and 5° on the measurements in SH5.

So my question is, is it even possible to get a somewhat accurate Fix without the aid of the Navigator? Are those Angle errors real or do I just make some stupid mistake? And if there are errors how to Correct for them?:06:

Thanks!:salute:

Ps. If you wanna try to calculate here are the numbers
DR: 55°48N' 3°46'E 8. Oct 1939 18:40
Polaris measured Angle: 49°50'
Mirach: 17°55'
Dubhe: 32°40'

[gap]

My guess is that the game knows your exact location but when asked, it puts a random figure into it to make it off some, instead of best guessing.

If memory serves me well, this is exactly how TDW implemented his DR/CF code: random deviation from the real (hidden) position. Ocean drifts are not modelled in game. Course deviations and speed drops are, but they are not considered for position fix calculations.


Especially, DR has too much course deviation. 90 degrees west is pretty damn close to 90 degrees west. 18 knots is pretty damn close to 18 knots, so travel for 10 hours west is not going to be off by 5 degrees and not away from target by more then a few kilometers. But DR can be off by way more than that. Like some first grade schooler done the figuring.

There should be an user option, accessible through New UI's options editor, for adjusting the maximum percent of deviation. :03:


my tutorial is almost done

Any news on it? :)

[Gauthier]

my tutorial is almost done

Hello,

any news?
G

[Gauthier]

Hello,

any news?
Tks a lot.
G

[Examiner2]

Is there any news on tutorials on how to calculate your position without using the navigator? I've been trying to search and learn how to calculate my position celestially and with dead reckoning. Are there any tutorials on how to do this?

[THE_MASK]

Is there any news on tutorials on how to calculate your position without using the navigator? I've been trying to search and learn how to calculate my position celestially and with dead reckoning. Are there any tutorials on how to do this?http://www.subsim.com/radioroom/showpost.php?p=1567713&postcount=34

[Examiner2]

http://www.subsim.com/radioroom/showpost.php?p=1567713&postcount=34

Thanks for the link but this isn't something that could help me yet. I'm looking for more of a real-nav for dummies kind of thing. I know absolutely nothing about marine navigation, so I need an in-depth tutorial on these things.

I did find a supplemental manual in the realnav folder "The Mathematics of The Longitude" which seems to have the information that I would need.

One last question, how do you bring up the sextant tool in-game? I'm using sober's mod list.

[THE_MASK]

Thanks for the link but this isn't something that could help me yet. I'm looking for more of a real-nav for dummies kind of thing. I know absolutely nothing about marine navigation, so I need an in-depth tutorial on these things.

I did find a supplemental manual in the realnav folder "The Mathematics of The Longitude" which seems to have the information that I would need.

One last question, how do you bring up the sextant tool in-game? I'm using sober's mod list.Use the options editor and enable the officers panel .