Celestial navigation by day

[Pilot_76]

Historically (and nowadays as well) how can you navigate during the daytime using only the Sun as a reference? I've read a bit about the noon shot (finding your long. at noon, UTC difference, 15 degrees\4 min etc) but in one of the movies at youtube a "simulated" cel nav fix was done at sunrise and at sunset. What's this for?

[kylania]

Someone linked a fantastic " " video here somewhere which explained the whole process. It relies on predetermined tables though - basically a list of the position of the sun at given times from given locations.

So you use the sextant to mark the sun's location at a specific time. You then estimate a location near to where you think you are given all the tables and stuff and figure out how far away from that point your assumed position is. This results in a line you could be along. Do it again an hour later (giving the sun time to move quite a bit) and measure it again, resulting in another possible position line. Where the two lines meet is where you are. At night you could simply take another reading from another star, but using the sun alone you need to triangulate via a second sun reading.

I guess the sunset and sunrise (and noon) checks are easiest since you're more likely to have knowledge of sunrise/sunset times then you are to have the multiple books of where the sun is at a certain time from the video?

[Pilot_76]

thanks for the info kylania, I am doing some experiments in SH4. BTW, do you apply Celnav in any SH? If yes what is your method?

[Rockin Robbins]

You can forget about the sky being anywhere near good enough in SH4 to do ANY celestial navigation from it. The only celestial navigation that can be done comes from knowing the position of the sub, putting those figures into a planetarium program and then doing the celestial navigation from there. SH4 was never meant to be a night sky simulation and it is not. It has a sky. That sky, especially solar system positions, is not accurate for date and time.

Typically, what is done with the Sun is meridian transit times. You have an accurate chronometer set for GMT. You get the time the sun passes its highest point. That is noon. The difference between GMT and your transit time is your longitude. This is not particularly accurate due to the size of the sun and the interpolation between precisely timed observations necessary to determine transit time. But it will get you in the same zip code.

[Arlo]

Originally Posted by Rockin Robbins

You can forget about the sky being anywhere near good enough in SH4 to do ANY celestial navigation from it. The only celestial navigation that can be done comes from knowing the position of the sub, putting those figures into a planetarium program and then doing the celestial navigation from there. SH4 was never meant to be a night sky simulation and it is not. It has a sky. That sky, especially solar system positions, is not accurate for date and time.

Typically, what is done with the Sun is meridian transit times. You have an accurate chronometer set for GMT. You get the time the sun passes its highest point. That is noon. The difference between GMT and your transit time is your longitude. This is not particularly accurate due to the size of the sun and the interpolation between precisely timed observations necessary to determine transit time. But it will get you in the same zip code.

I think I'm missing something here. What's the point of celestial nav in SH if the map is spot on?

[Sailor Steve]

Originally Posted by Arlo

I think I'm missing something here. What's the point of celestial nav in SH if the map is spot on?

The point is that the map is indeed spot on. It's impossible to be out of position by even one mile, whereas in real life navigation isn't perfect. It can be very close, but seldom perfect. The other half is that when you can't see the sky you have to use dead reckoning, which is the knowledge of your speed and course applied to your last known position, which is prey to currents you can't see. Some people want that uncertainty, and some want to actually navigate their boat.

[Arlo]

Originally Posted by Sailor Steve

The point is that the map is indeed spot on. It's impossible to be out of position by even one mile, whereas in real life navigation isn't perfect. It can be very close, but seldom perfect. The other half is that when you can't see the sky you have to use dead reckoning, which is the knowledge of your speed and course applied to your last known position, which is prey to currents you can't see. Some people want that uncertainty, and some want to actually navigate their boat.

That doesn't appear to be a point as much as a desire. Celestial navigation isn't needed in SH4 and wasn't part of the game's realism settings. I'd like to be able to explore my submarine from stem to stern but there's no point in it, game-wise, because it's not necessary. Now, immersive role-play wise, it'd be cool but if it's not practical to mod or implement then there's no point in asking for it as much as there is in daydreaming about it with other sub-simmers here.

If it does become a mod, well, honestly, there's a few desires I have that outweigh shooting an azimuth in between missing targets with my torpedoes. But to each their own and I'm not one to spray on anyone's celestial parade.

[Rockin Robbins]

Arlo, I wouldn't mind the ability to do celestial navigation if it were possible in-game. What's being done now is that people have turned off their position indicator in the nav map. Then they feed the game position to a separate planetarium program. Apparently they even have an in-planetarium sextant so you can actually simulate taking a sight. Then, after doing the calculations to obtain longitude and latitude for your sub, you go back into SH4 to plot the position.

Unfortunately, you also give up the ability to track target positions relative to your boat because there is no indicator for your boat's position. You just end up giving away three times more authenticity than you gain.

If you're not playing the game as such and just want to learn celestial navigation it's a great practice tool.

But in-game our sky isn't good enough to navigate from. I've demonstrated that moon phases and positions are totally wackazoid. You see, I have some of those whiz bang planetarium programs, Maurice Chevalley's Sky Charts (highly recommended and free!) and The Sky for Windows by Software Bisque.

[Arlo]

Originally Posted by Rockin Robbins

Arlo, I wouldn't mind the ability to do celestial navigation if it were possible in-game. What's being done now is that people have turned off their position indicator in the nav map. Then they feed the game position to a separate planetarium program. Apparently they even have an in-planetarium sextant so you can actually simulate taking a sight. Then, after doing the calculations to obtain longitude and latitude for your sub, you go back into SH4 to plot the position.

Unfortunately, you also give up the ability to track target positions relative to your boat because there is no indicator for your boat's position. You just end up giving away three times more authenticity than you gain.

If you're not playing the game as such and just want to learn celestial navigation it's a great practice tool.

But in-game our sky isn't good enough to navigate from. I've demonstrated that moon phases and positions are totally wackazoid. You see, I have some of those whiz bang planetarium programs, Maurice Chevalley's Sky Charts (highly recommended and free!) and The Sky for Windows by Software Bisque.

If someone can guru a mod that can make it come to pass, I'm good with it. Alas, I'm also good with no mod of this nature surfacing (currently - ya never know what I may get a hankerin' for the next day). It's pretty skies (or stormy, which, well, as long as I'm not really cold and wet, is pretty too) and water breaking over the prow and I'm good with that. What would really float my boat, so to speak, would be the ability to do some shore fun - both as part of a party sent ashore in combat or on liberty. And it would be fun to have the ability to form and join a boarding party (on those oh so rare occasions that a sub got to board a combatant).

We all got dreams and I support all of em ... just mine more. But until I become a modder all I am is a voice in the peanut gallery. Well, I guess even if I manage to mod, I am.

[kylania]

Originally Posted by Pilot_76

thanks for the info kylania, I am doing some experiments in SH4. BTW, do you apply Celnav in any SH? If yes what is your method?

I don't use it in Silent Hunter 4, but Silent Hunter 5 has a very robust Real Navigation system. I'm still not that good with finding my location via sextant, so I rely on the navigator, but it's still a fun experience.

[Arlo]

Well, I may reconsider. Anything with the word sex-tent in it is worth exploring if there's a co-ed crew (that was bad but then I'm not known for the best puns).

[Sailor Steve]

Originally Posted by Arlo

That doesn't appear to be a point as much as a desire.

Absolutely true, but also true of manual targetting and a host of other options. Some people want to do it.

What I would like to see in a sub sim is semi-manual everything. When the weather is clear you follow your listed waypoints. When it's not so fine there is a chance the boat will get off course, but the chart will still show you on track, until the next clear day and then you find out where you really are, and lay new waypoints. Same with targetting. You get the range and bearing yourself from the periscope, and the target's estimated position is drawn on the map. You do it again, and it's more accurate. The more you do it the better the solution is. Of course, as with navigation, you might still be off.

[Arlo]

Sounds interesting. But then it becomes a matter of what may or may not be a practical investment for those wonderful modders. Can it be done? Can it be done easier than a mod that'll let me play acey-deucey in the crew's mess? I may hafta put up or shut up and learn to mod my ownself. (But I'd download a 'celestial nav' mod to give it a go if someone else invested their time on one for the sake of the community. As long as it's TMO 2.2 compat.)

[Rockin Robbins]

I'm afraid all this stuff is hard coded in the .exe files. Modding those isn't modding, it's illegal hacking, so you have two choices as a modder.

Choice 1 is to turn off the sub position symbol on the nav map and attack map, find the sub position in the game files and feed that to an exterior planetarium file. That's what has been done by the navigation mod people for SH4. In doing so you give up a ton of realistic and useful things......like the ability to attack and sink opponents. This is not a workable scheme to my way of thinking other than as a proof of concept and a navigation trainer.

Choice 2 is not to do celestial navigation in SH4. That's been my path.

Or you could go to door #3 where the object of the game seems to be walking around your sub asking how the soup is for the ten thousandth time to build morale, while playing a bizarre Frankenstein poorly executed submarine meets horrible parody of the Sims monster. I'll pass on that one too. I could care less if Johan's girlfriend is pregnant with kittens.

[Arlo]

Originally Posted by Rockin Robbins

Or you could go to door #3 where the object of the game seems to be walking around your sub asking how the soup is for the ten thousandth time to build morale, while playing a bizarre Frankenstein poorly executed submarine meets horrible parody of the Sims monster. I'll pass on that one too. I could care less if Johan's girlfriend is pregnant with kittens.

Hehehe .... loud and clear.