Bearings in space

[Lord Carnifex]

We may have wandered from the original question, though. My 3e GURPS Space (Steve Jackson and William A. Barton, (c) 1988) says

Originally Posted by GURPS Space, p.98

...the direction from Sol to the Core is defined as Galactic North. Galactic Up is arbitrarily defined; if an observer is "above" the Milky Way, the arms go counterclockwise as they spiral outward from the core.

Is this in the new edition of Space? And are these terms used in rela world astronomy, does anyone know?

[Anthony]

Originally Posted by Lord Carnifex

And are these terms used in rela world astronomy, does anyone know?

Galactic north has a meaning. It seems to be what Space is calling Galactic 'up'. Coreward is galactic longitude 0

[Anthony]

Originally Posted by Agemegos

That isn't a relativistic effect. But if does suggest that S Doradus might not be a perfect choice of 'landmark'.

Depends on whether it vanishes within a hundred thousand years or so, which is something that, given FTL, can be determined fairly quickly.

Given a bit more time, you can probably locate the black hole at the center of the Large Magellenic Cloud. That's not going away any time soon.

[Lord Carnifex]

Originally Posted by Agemegos

<snip>
The problem involves the simultaneous solution of a number of equations (non-linear ones involving the trig functions). That can be done by successive approximation, but it far more efficient to use mathematics.

Very well done. This must be why I'm not a professional astrogator/astrogation computer programmer. I must admit I did miss the more elegant mathematical solution here.

[sjard]

Not on topic I know, but every time I see this thread title my first thought is that it has something to do with using ball bearings as weapons in space.

[LoganSaj]

Well, really all I need is something for dialogue purposes. I don't want to wing it. I want to use something that actually has some merit to it.

For example, what would be an efficient dialogue for a sensor operator warning of a unidentified blip 3 miles to the right of the vessel, 1 mile down, and on a tangent course?

I'm sure if I want to pull a Star Wars "wing it" / ad lib type dialogue, the NPC or player could simply say, "Bogey, at 0-53". But ... what the frak does that mean? I would prefer an actual system, even if it's simplified.

[William]

Originally Posted by LoganSaj

For example, what would be an efficient dialogue for a sensor operator warning of a unidentified blip 3 miles to the right of the vessel, 1 mile down, and on a tangent course?

I'm sure if I want to pull a Star Wars "wing it" / ad lib type dialogue, the NPC or player could simply say, "Bogey, at 0-53". But ... what the frak does that mean? I would prefer an actual system, even if it's simplified.

On the local scale, just treat bearings relative to the ship. Take a line straight forward from the ship. An object is at some number of degrees port or starboard of that line (up to 180 degrees, a.k.a. 'aft' or 'dead astern'), and a number of degrees elevation, positive 90 to negative 90.

"Bogey 40 degrees to port, 20 degrees elevation" might get shortened to "Bogey, port 40 plus 20." For detail on its current relative heading, its directions of travel might be "closing", "orbiting" or "moving away," "heading to our port or starboard," and "climbing" or "diving."

[malek77]

I think there may be two things here getting mixed (into a deliciously scientific slushie!) - which boil down to piloting the ship and navigating the ship. The following is from wargame-design experience in trying to keep it simple.


For general GMing use, I'd want something that orients everything else to your ship. ie: "Bogey detected at +25°, -35°, range of 500", where "0°,0°" is directly ahead on your current course, + is to the right/starboard, and the second digit is the detected objects elevation.

At +25°, -35°, that's ahead and a little to the right, but well below and 500(units) away...

Maintaining accurate ranges wouldn't be impossible, but would require some fast trigonometry.




(If you want to accurately map everything in 3d (such as for a dogfight), I'd use a 2d grid to act as the X,Z plane, and book-keep Y axis seperately. The origin point is arbitrary. You maintain values of your speed in the 3 axes, and simply add them on with any acceleration each turn.)




Navigation is a whole different beast, and has been well covered in the other posts.

[ericbsmith]

Originally Posted by William

On the local scale, just treat bearings relative to the ship. Take a line straight forward from the ship. An object is at some number of degrees port or starboard of that line (up to 180 degrees, a.k.a. 'aft' or 'dead astern'), and a number of degrees elevation, positive 90 to negative 90.

"Bogey 40 degrees to port, 20 degrees elevation" might get shortened to "Bogey, port 40 plus 20." For detail on its current relative heading, its directions of travel might be "closing", "orbiting" or "moving away," "heading to our port or starboard," and "climbing" or "diving."

The Star Trek Next Generation Tech Manual describes a system where dead ahead is 0° by 0° (000 mark 0), with the bearing continuing all the way around the ship up to 359° by 359°. Azimuth (right/left rotation) comes first then elevation/declination.

Thus a course of "24 mark 35" means 24° to the right of the current course, 35° up above it. Since the numbering continues all the way around, this means that in the azimuth 90° would be a course directly to the right, while 270° would be a course directly to the left, 180° would be directly behind. An elevation of 90° is straight up, 270° straight down, and 180° straight behind.

[LoganSaj]

Excellent! I really like those ideas, EricBSmith and William. I wonder if there is a way to incorporate them together, or use the pros of both together ...