With regard to 'shooting' the stars and sun. You usually set yourself a disciplined timetable, but the weather can play havoc with this, so you must be able to take a reading at the best opportunistic moment - therefore no restrictions on where and when.

As an example:
In SH3 I set out from Kiel and set course to go around Scotland, down the west coast of Ireland. One day out from Scotland the weather closed in, and that was my last reading for about 4 days
I was then navigating on Dead Reckoning - course, speed and time, from my last know plot. I managed to get pass Scotland and was going south on the west coast before I got my next plot, some 4 days later. By dead reckoning I was about 50Nm out, and so corrected my course to go pass some small island.
I passed that island 24 hours later, 1 hour later than eta and about 5nm to far west.

This was my first RealNav attempt and ... I was chuffed :)
The only thing missing in SH3/4 are currents, tidal and otherwise. It'll be nice to have these.

i don't have SH5 (DRM @#!$!@%) but in SH3/4, Real Nav implied, no sub icons.. anything that gave you subs position away on the map.

hello vanjast,

you should rethink about your sh5 policy. the user "thedarkwraith" has written a genious mod where a real navigation feature is implemented. because of less modding restrictions, he is able to code in most of the features requested by the community. real navigation was one of his last efforts, it is brilliant! your sub icon is away. you can ask the navigator to give a celsetial fix or to use dead reckoning, he gives you the position directly to the map. errors depends on weather (celestial fixes) or time and distance (dead reckoning). you can draw in nav marks by yourself and write some info directly on the map. also course changings as a result of wind are part of sh5, so real nav becomes a new dimension here. a sextant can be used too, but i am not using it yet. that was the reason i was asking how often we can use it.

@tdw: i think we have to restrict the rules the celestial fix can be taken. clouds f. ex. are a "nogo" for celestial nav...

any kind of rain or overclast clouds make celestial navigation unavailable (already coded in). Do we need to enforce some other restrictions on celestial navigation? :hmmm:

you shouldnt define the conditions, when real navigation doenst work. you should define conditions, when it runs (sun must shining on day, stars must be visible at night) these conditions are not often available... and as i understand it right, on day you need sunrise, sunset or noon.
like vanjast descriobes it: dead reckoning is the normal use of navigation, celestial navigation fixes will be taken whenever its possible (not very often)

I'll clarify for you. Please excuse the long winded explanation. Hopefully by the end of it I will have answered your question adequately.

First we'll look to the Admiralty Manual of Navigation Vol. I to define an important term: position line; "A position line is any line, drawn on the chart, on which the ship's position is known to lie. ... The simplest form of position line is the line of bearing obtained from a terrestrial object of known position."

Position lines can be obtained from various sources, be they bearings to known objects, distances to known objects, or some other accurate source. When two or more position lines cross, the point at which they cross is called a fix. Navigators "fix" the ship's position on the chart by obtaining position lines by various means and plotting them on the chart along with the time the fix was taken. A fix can consist of position lines of any source, so long as they are obtained and plotted accurately. Navigators then "dead reckon" the ship's current or future position by using the ship's speed and course, and the set (estimated or known drift) to plot a line on the chart that represents the ship's course made good, and to calculate a speed made good.

It's important to remember that a fix always represents the ship's position sometime in the past. As soon as the fix is plotted on the chart it is already obsolete. This is because, unless the ship is perfectly stationary, the ship has moved some distance along its course made good in the time between the navigator's observations and when the fix was plotted.

Celestial navigation uses measurements of celestial objects to obtain position lines which can then be used to create a fix. The navigator calculates the altitude and bearing at which an object should appear from a certain assumed geographic position at a certain time. Then, using a sextant, he observes the object's actual altitude at the time noted from the calculations above. He can make the observation first and then do the calculations, but the times used for each calculation must match the times of each observation precisely. The navigator obtains a position line by noting the difference be between the calculated and observed altitudes of the object and then plotting that difference on the chart as a distance in nautical mile along the object's calculated bearing from the ship's assumed position. From this point on the chart the navigator draws a line perpendicular to the line of bearing to the celestial object. This is the position line.

Simple, right?:yeah::har:

These calculations must be performed for each line of position obtained. This means that for a Navigator to obtain a fix using only celestial objects he needs to spend about an hour at the chart table (20 minutes per line, three lines for a "cocked hat" [more certain position than just two lines]).
But in the middle of the ocean with no GPS, spending an hour to get a reasonably accurate fix was well worth the time. The down side is that the navigator was generally lucky to get a fix once per day.

You see, to get a three point astro fix, you not only need to be able see at least three celestial objects in the sky at the same time, but you also need to be able to see the horizon too. If it's too light objects like planets and stars are invisible; too dark and the horizon disappears.
Morning and evening twilight is when the navigator gets the best fixes.

There are ways to obtain fixes at other times during the day, most notably midday. I won't go into that in great detail except to say that with an accurate timepiece one can accurately measure the time at which the sun crosses the southern meridian. Almanacs are then used to obtain a longitude.

Hope this answers some questions folks have about astro.

Cheers

a big thanks for this explanation. for the mod, some details should be changed, i think. if the navigator is happy to get one fix per day, it should be the same situation in the game. perhaps, the button "get a celestial fix" is only available 3 times a day? or the conditions for beeing able to press the button must be more restricitve: best weather conditions are needed. perhaps tdw can change this?

I can make it do anything I want. We just all need to agree on what the conditions are :yep:

I will,.. but only when.... :D it's a matter of principle, and an experten Kaleun does not lower his standards :03:

When this happens Darkwraiths mod will be the first I'd try..:03:

You certainly need visibility to get out to the horizon. And you also need a sky that's clear enough to see three navigational stars. The sky doesn't need to be absolutely clear. But scattered cloud would certainly give more opportunity for fixing than a broken ceiling. Bear in mind also that the sun and moon are often available during the day for a quick two line fix. Perhaps it would be enough to have a "get astro fix" button that's visible both when the weather conditions are good enough, not necessarily perfect though, and from between morning nautical twilight and evening nautical twilight. (about an hour before sunrise to an hour after sunrise). The button should also gray out and not appear again until the fix is on the chart depicting your ship's position at the time you pressed the button.

hey vanjast,

tdw and some guys are discussing real navigation and tdw is implementing this feature to his mod. what we need are more experts who can give advise concerning real navigation. buy it and help us making a good real navigation mod. because of the script possibility, everything is possible to implement. you will be surprised, what tdw can do. we only need ideas and testing guys...

If it helps, I'm a serving naval officer. I can probably answer most of your questions about navigation.

I was referring to SH5's DRM... I cannot be much help with a mod until i have the game, which I won't have while DRM is present .....

I'd like to see pics of the mod and ideas though... maybe I can provide some input.
:)

Check the messages of the user don1reed in this thread:

http://www.subsim.com/radioroom/show...47#post1558947

Specifically post 154 and the 2 following. He has much personal experience in celestial navigation, and applied it often in the game (in as much as SH3 and SH4 allowed).

First real Navigation with help of dead recon, sunset- and celestial-navigation.
xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx xxxxxxxxxxxxxxxxxxxxxx
(1)
4 1/2 min after Sunset near Bornholm (in the right side of the photo) at real position 55.00,00N 15.00,00E
http://i714.photobucket.com/albums/w...1/SH5Img02.jpg
I read a sunset (upper-limb of the sun fully disappears behind the horizon) at 18:15:50 GMT.
But at my actual position of 55.00,00N 15.00,00E the sunset had to be at 17:53:00 GMT according
to this
http://i714.photobucket.com/albums/w...1/SH5Img05.jpg
http://www.srrb.noaa.gov/highlights/...e/sunrise.html
Sunsetcalculation for a specific time and location.
So this gives me an error of 5°40' because the sunset at 18:15 GMT for Sep 02 1939 is at location 009°20E, 15°00N which gives me an
error of 361.3 km ( http://www.movable-type.co.uk/scripts/latlong.html ).



(2)
Actual Moon at 02-Sep-1939, 21:00 local time
http://i714.photobucket.com/albums/w...1/SH5Img03.jpg
The moon-display could be correct because the correct phase of the moon
(according to http://www.maa.mhn.de/StarDate/moon1939.txt ) is
Full moon 29-Aug-1939, 22.16
Last quarter 06-Sep-1939, 20.41.


(3)
Celestial navigation with Polaris (north star).
Polaris + sextant gives me a position of 53°09N.
http://i714.photobucket.com/albums/w...1/SH5Img01.jpg
The reading was 52.15 + 1 (correct the misleading of polaris) = 53.15 = 53°09'.
But i am at position 55°00N. So the Polaris gives me an error of 1°51' = 205.7 km.
( http://www.movable-type.co.uk/scripts/latlong.html )



(4)
My Route with dead reckon-navigation in real time:
http://i714.photobucket.com/albums/w...1/SH5Img04.jpg
The fact that i reached Bornholm (that was my intention) surprised me and was not so bad.

pretty cool! The integrated mod of Otto's chalkboard in my UIs mod has a sunrise/sunset/moonphase calculator built into it. You access it by pressing shift+B :yep:

Didn't know that. Thxs.

Ah.. thanks for the pics...I see not much has changed since SH3 days :)

This is interesting stuff.

Does the in-game sextant work like they do in real life?

In other words, can I use the real-world navigation links provided earlier in this thread and just use the tools in game to get a fix, or do I have to apply some other techniques to compensate for any in-game limitations on the SH5 sextant, sky, celestial bodies, etc?

yep.
(1) vertical sextant angle for coastal navigation: here distance-measurement
http://i714.photobucket.com/albums/w...Sextant_01.jpg

(2) horizontal sextant angle for coastal navigation: here measure the
angle between 2 points (lighthouse, factory)
http://www.tpub.com/content/administ...4220_238_9.jpg

http://i714.photobucket.com/albums/w...Sextant_02.jpg

(3) Vertical sextant angle for moon/star/sun-shoot.

1 and 2 working pretty much out of the box. For 3 it depends on your screen-resolution. A rework of the sextant correspond to your screen resolution is probably necessary. For good accuracy many uses the program stellarium. Also what you need here is definitely a nautical almanac of 1939 resp. 1940 or later or a program that creates nautical almanac data.

can anyone tell wich mods I need from DKW s ui mod for real navigation (in addition to real navigation)? I have a pretty good idea but he just said no mapupdates etc etc...do I put them behind the megamod?can I put in hole of dkw s ui mod maybe just to be sure ? I get confused what is the actual mod and what are add on mods but I ll have a closer look at the files there.