Howdy gents,

I'm not a modder, I'm a navigator that still uses cel nav with sextant and nautical almanac to pinpoint my location on spaceship earth.
I've been subsimming since C64 days and my fondest wish was to someday be able to reinact navigation via virtual sextant and nautical almanac within a subsim before I made my final voyage.

Like many of you, I've tried to measure the angle of celestial bodies above the horizon with all sorts of gimmics and gadgets using SH1 to SH4.
I've used Virtual Sailor 7 (VS7) as it has the most realistic sextant to date, (it measures the angle of elevation to 4 decimal places) and it too is not accurate. VS7 has the stars on a separate transparent sphere from the separate transparent spheres that depict the sun, and the moon, and the planets. Each sphere is revolving around the users position, supposedly, on their rightful jouneys throughout any year or time period the "user" decides to sail.

The designer of VS7, alas, has paid more attention to the GPS configuration than that of Celestial Navigation's adherence to Nautical Almanac predictions.

I can only take my hat off to anyone of you modders who can get the job done; but, all we users are interested in is the War years between Sep 1939 to Aug 1945. The celestial ephemeris doesn't have to be compiled for a century.

As I have mentioned in other threads concerning this topic, navigating to within 30 nm is not nearly accurate enough. The Kreigsmarine and Allied Navies of the period were able to navigate within 0.5 MOA (1/2 nm)using the navigational instruments of the time.

Best wishes to you all. Your efforts are being followed closely and with great interest.

Tnx,

@don1reed

I'm thinking about getting a copy of VS myself, but I'm not really convinced, yet.

Did you try cel nav in MSFS already?

http://www.swiremariners.com/sextant/index.html

Hallo Nico,

No, I've not tried it yet; however, what you've provdided looks very promising. :up:

The sextant in VS is extremely well made and the concept is good; but, the celestial spheres are out of sync with reality and sometime will put the mariner 200 nm off. It would be wonderful if the sextant in VS could be adapted for use with SH3 & 4.

Cheers,

If you want to try out FS9, make sure that you install a better night sky set, like this one:

http://www.elbiah.de/flusi/MyFsStars/MyFsStars.htm

Regarding VS, it's too bad to hear that even a simulator dedicated to realistic navigation doesn't get it right. I think if we can achieve 30nm precision in SH3, it is certainly not that bad. Search areas will still be quite manageable, I think. I mean, more often than not the u-boats had to rely on dead reckoning for days, sometimes even weeks. It's certainly no showstopper for me.

*SNIP!* I think I got it! The solution for a sextant, I mean! All we need is a way to measure the amount of mouse movement in y-axis, from the horizon up to the object of interest! I recommend using the stabilized obs scope on high power for this. I think an external application could handle this. This application runs in the background, and when the user aligns the scope with the horizon, he presses a key combo that starts the measurement. The keys remain pressed until the scope is aligned with the object of interest and are then released. The application now reads the mouse movement in y-axis in the moment of pressing and releasing and converts this into degrees of elevation.

The benefits: a relatively high level of accuracy, in the range of 0,1° I think. No 60° limit, no swaying field of view.

There are two problems, though: 1. we need a coder! 2. Initial calibration by the user is required.

What do you guys think?

Excellent idea Nico!

Calibration is always required in RL, as you know.

The mariner/navigator must perform three tests with the sextant before using:
1)Test for perpendicularity of the Index mirror.
2)Test for perpendicularity of the Horizon glass.
3)Test for parallelism of the Index mirror and Horizon glass.

These test are not performed each time a sextant is used but at least on a scheduled basis for preventative matenance.

Index Correction (+/- IC) however, must be determined with each use. It is usually accomplished by viewing the horizon with zero degrees on the arc to see if the horizon is on or off the arc when viewed through the horizon glass.

An upper limb (UL) sight is less often used with the Sun but is often necessary with the Moon since the lower limb (LL) may not actually be a circular one, depending on the phase.

Good idea. Could be problems, though. For example, some mice have an acceleration feature which can be configured to the users taste, and which would mess up the readings. Also FPS/lag may have an impact, depending on how the game is coded.

Sounds like a minefield to me but maybe I'm just a half-empty kinda guy. :hmm:

OLC,

Would those mouse problems still exist if the player were viewing through the Obs/Nav scope? In other words, when viewing through the Obs/Nav scope
view the horizon...calibrate
rotate the scope upward to the celestial body
then measure the altitude
?

I am aware that there might be problems. But without a coder this discussion is moot anyway. Personally, I never got past "Hello World!", despite the excellent literature that is collecting dust on the shelf (i.e. SAMS C++ Primer Plus 5. Edition - what a tome!).

As for mouse acceleration, I think it can be handeled with a log scale instead of linear coordinates. In fact, the different mouse settings (acceleration, resolution, etc) are the main reason why I said that it requires calibration!

I think so, yeah. Unless SH3 ignores the mouse settings, which it might for all I know. Or alternatively, if this new tool takes account of the settings that'd do the trick too. I'm just trying to give a heads up.

Mouse acceleration makes the mouse move further when you move it faster. So if I move it 2cm slowly, the cursor doesn't go as fars as if I move it 2cm quickly.

And of course there's the normal mouse speed setting to consider.

Also in many games the resolution of the screen actually has an impact - something to consider if you want this tool to work with the high res fix.

As long as such things are taken into account I see no reason why it shouldn't work. Like I said, just trying to be helpful. :)

OIC - no worries then :)

BTW this is a bugbear for me because I like first person shooters but every time I install one it's inevitably got it's own ideas about what 2cm of mouse movement means, and whether or not it feels like paying attention to my windows mouse settings :damn:

Edit: sorry, OT.

A possible workaround might be to temporarily disable the mouse acceleration in Windows setup. A small price to pay, IMO. The rest is subject to further testing!

The distortion you have mentioned was the reason why I gave up on it earlier. But as the amount of distortion is always the same, it can be taken into account (the same applies to mouse acceleration!)! Let's say we use the method I have suggested, you would do the calibration by shooting 4-5 stars at different altitudes (in a special "calibration" mission file where the exact altitudes are known and used as reference constants). With a number of readings at different altitudes it should be possible to get a calibration curve (hell, I did this for a living once in chemistry! I dreamed of calibration curves after a while!). Now the computer can take care of the rest.

True. Should work. Could also work for the other method :)

In the lab we had a neat little shareware program that could automatically calculate the correct curve after we entered the measurement results of our test series and calculate a formula that exactly described the resulting curve for later use. It should be handy here, but I don't remember the name! :oops: