Celestial Navigation in SH4

[don1reed]

Howdy, berobispo.

Always use GMT for navigation. Its the time system all the modern almanacs are setup for.

Cheers,

[berobispo]

thanks for the quick answer!

but: is the question finally solved if SH3 gives me the real GMT? Or is it not that important when doing star sights?

and: any simple to grasp tutorial on this topic?

thx!

[Dutch]

Holy Cow........Fantastic work gentlemen! Would be nice to see if SHV will be a bit more modifiable in this department but out standing work as it stands here.

[berobispo]

about GMT: I made some custom missions and (I think)found out:

-normal time (time shown without mouseover) is GMT, mouseover time is sh3 timezone time. they start at 7°30' from 0° and are 15° wide. gmt and local time don't change when saving/reloading.

-when going west, the game simulates the earth's rotation pretty well, I could pinpoint my location to about 15nm just by using the charts for sunrise/sunset provided by vanjast. given the fact that i can't measure seconds and the sun's upper limb is not always easy to discriminate I find this quite good

-when going east on the other hand, things are different. I was as far as 25°E and my local sunrise occured 25 min earlier then it was supposed to at 0° <-- should have been 1h40min if I'm not mistaken. --> it is completly unfeasible to use the ingame sun to determine local apparent noon when going east

I ended up with the following plan for real navigation (one reason: current career in the med):

save a game at approxiomately local noon, run don1reed's python script and enter a gmt time that I reason to be before my local noon, go to stellarium and do a noon sight. this works a little bit of cheating because stellarium has a fixed position and the time entered doesn't change my position etc., but IMHO the best way to go. maybe I'll even try 3 star fixes, but no idea how. maybe using nautictools.de, altough I'd rather like to at least try to do the numbercrunching on my own...

[Pisces]

I uploaded all the neccesary files I could think of. My harddrive is a mess.

Bunch of files with the tutorial, almost everything you need:
http://www.filefront.com/14996485/Ce...ion-for-H4.7z/

Almanacs for both SH4 and SH3:
http://www.filefront.com/14996507/19...5-Almanacs.7z/


Updated sh4tostellarium program: reads savegame to create stellarium config file (but I think Stellarium doesn't work anymore with the config/script-file system that Mike made it for since some version.. maybe you can find an old version of Stellarium somewhere... or be a daredevil and code a new program that makes it work)
http://www.filefront.com/14996519/sh4tostellarium.7z/

Navcharts for SH4 (if you don't want to clutter the game map):
http://www.filefront.com/14996653/SH4-Nav-Charts.7z/

Leech them while they are there. It's on Filefront, so there is no garuantee how long.

[I'm goin' down]

I do not know the first thing about navigation. If the links are repaired I will take a crack at it.

[Pisces]

Well, those links are the same files that 6SJ7GT posted. You can check inside the archives and notice the dates are all from that timeframe. I never touched them.

[6SJ7GT]

Thanks for uploading a copy of my files, Pisces. I have put them in my filefront area at:

http://www.filefront.com/user/6sj7gt

I added the 1939 - 1941 almanacs to the master file. At the moment Stellarium 9.1 seems to be easier to use. When I figure out how to get the location into the newest Stellarium I'll upload a program for that, (latitude and longitude command line options don't seem to work).

Mike 6SJ7GT

[I'm goin' down]

I am go to require some serious sit down time with this program. I am lacking is fundamentals, which might be math related, but I am not sure yet.

[Pisces]

Originally Posted by I'm goin' down

I am go to require some serious sit down time with this program. I am lacking is fundamentals, which might be math related, but I am not sure yet.

Nahh, looks worse than it is. Just a matter of adding and subtracting and looking into tables if you want to do it the hard way. Use the online almanac if you like to keep it simple:

http://aa.usno.navy.mil/data/docs/celnavtable.php

[CNA0]

At the moment Stellarium 9.1 seems to be easier to use. When I figure out how to get the location into the newest Stellarium I'll upload a program for that, (latitude and longitude command line options don't seem to work).

Mike 6SJ7GT

I've installed Stellarium 0.10.2 and, actually,"startup.ssc"(with lat-long coordinates and GMT date and time introduced by "Sh4toStellarium.py") doesn't have any effect.
I've observed that Config.ini keeps "Paris" as "location" in [init_location] block.

Is it any other solution than "manual mode"?

I can't find any tool (sextant) in Stellarium to read a star altitude. How can you read it?

[Pisces]

For the 'sextant' measurement you need to press the 'z' button. Then you get the azimuth/altitude grid. Then you have to zoom in on the celestial object and 'shoot' against the nearest gridline.

I too had trouble getting Stellarium to accept a long/lat position through commandline parameters and config file. But the manual explains not everything works completely yet.

Maybe it's possible to add a 'city' location to the list with the sub's coordinates. And have Stellarium remember that as default location instead of Paris.

Unfortunately the older version (0.9 something) doesn't work with vista. Or my system anyway.

[6SJ7GT]

Cnao,

I just got stelarium 10 working. there is a file "Sh4tostellarium10.py in my Filefront page. Try that one and let me know if it works for you.

a couple of other things to do, is set the altitude default to 0 meters and the time_zone to gmt in the stellarium config file. This doesn't seem to affect the azimuth angles for the stars though.

Pisces, if you click on a star the information on altitude/azimuth is in the upper right corner. If the clock is ticking the numbers change fast enough that getting the altitude/time right on gives a small margin of error.

Mike 6sj7gt

[I'm goin' down]

Why?

[Pisces]

Originally Posted by 6SJ7GT

Pisces, if you click on a star the information on altitude/azimuth is in the upper right corner. If the clock is ticking the numbers change fast enough that getting the altitude/time right on gives a small margin of error.

Mike 6sj7gt

Yeah, but this is hardcore navigation, right? We got to create some means of measurement error in this method. The deck isn't even moving. Besides, I'm sure Don1reed never saw digital numbers rollover in his eyepiece.