Re: Bearings in space
 

I believe we basically used the same system. ^_^ I used -90 to 90 for elevation, and Eric (or, Star Trek) used 270 to 90. Theoretically, there's another half a circle behind us (Eric's 180-degree elevation), but in practice you almost never use those coordinates since that gives every point in space two names.

Usage of the term "mark" to separate azimuth and elevation numbers is probably wise, especially for reports like "Bogey 40 mark 2, 500 meters and climbing." Aurally, it's a good sharp divider.

Re: Bearings in space
 

No, he's correct (if perhaps he explained it a little simplistically). If you use a full 360° coordinate for the azimuth (right/left rotation) you only need use a +/-90° elevation/declination (180° total). This is, in fact, how we designate location on the sphere we call planet Earth - if you imagine the "ship" is the center of the earth, pointed directly at the equator (0° latitude), and at 0° longitude.

The only thing using a full 360° elevation would truly give you is a very quick estimate of whether the object is in front or behind the ship - but a person trained to use such a system should already be able to tell that from the azimuth coordinate.

Re: Bearings in space
 

Hi,

I think we shall separate two case: first when your campaign will happen in one particular galaxy like Milky Way. And the second when your campaign will be inter-galactical.
In first case I think very obvious that the travellers will use their galaxy's center as reference. The x axis could be the line through the center and our sun, the y axis perpendicular with that through the center and the z axis is perpendicular both of the previous through the center of the galaxy.
In second case the things are not so easy. I think the only possibility to use the known universe's center but maybe that's too difficult to pinpoint.

Re: Bearings in space
 

I think we actually have three different cases:

First, we have campaigns set in what would be a small piece of the Galaxy. I have one setting where the "frontier" is 20 lightyears from Earth, due to the very slow FTL methods used. These campaigns would likely use the position of the homeworld or ruling world (if different from the homeworld) as 0,0,0 on the X,Y,Z axii respectively, with the XY-plane being the angle of the orbit of the homeworld around the sun. Even Star Trek's Federation uses this method; the Federation doesn't control the entire Alpha Quadrant, after all, and started with a much smaller area. Remember that habits are hard to break (we're still using a degree system, developed at least 6,000 years ago in Sumeria, despite the relatively recent inventions of radians and gradians).

Second, we have the galactic-sized campaign (common for Star Wars and other sci-fi/sci-fan settings), which uses the first method you mentioned. Even then, this doesn't always hold water; in Star Wars, whose system has been in use for 25,000 years, Coruscant (believed to be the homeworld of humans, and capital of the Galactic Republic (and later the Empire and New Republic)) is 0,0,0 on the starcharts, not the black hole at the center of the galaxy.

The third is the intergalactic set up. Even there, we have two set-ups.

In a campaign where galactic-level interstellar FTL is around, you will have the main galaxy and its satellite galaxies (example: our Milky Way and the Megallanic Clouds). Here, the system used for galactic-sized campaigns can be used.

In a campaign that spans something like the Local Group of galaxies (Milky Way, Andromeda, and M33, along with the satellite galaxies and other irregulars in between), the best thing to do is to assign a single galaxy as the "center", and deal with the center of that galaxy as 0,0,0, calculating from there.

It may even be possible for all three of these methods to be used in a campaign; one system for long-range intergalactic travel, one system for galactic travel, and one system for galactic sector travel.

Re: Bearings in space
 

I agree a small scale campaign will probably use Earth or some other reference world as the origin, but the XY-plane need not necessarily be the orbital plane of the reference world. Having a central origin makes for easy math by keeping the numbers small; which way the plane is oriented doesn't really matter. Any one of the reference planet's equator, reference planet's orbital plane, or the galactic plane would be equally likely. Actually scratch that; the most likely is all being used to some extent, with potential confusion if maps aren't labelled accurately.

Re: Bearings in space
 

The biggest problems with using the planet's equator as a reference for the XY-plane are two-fold:

First, as the planet orbits the star, the actual location of the equator changes minutely; the equator is rarely on the same plane as the orbit, causing seasons. This doesn't mean much, but can lead to inaccurate astrogration.

Second, the planet wobbles over time, causing what folks on Earth call precession. Polaris hasn't always been our pole star; during the time the Great Pyramids are commonly believed to have been built, Sigma Draconis was the pole star. In another 16,000 years or so (I'm fuzzy on the actual time frame), Vega will be the pole star. Imagine setting a trip for 0,0,30, intending to hit the vicinity of Polaris and hitting Vega's neighborhood instead.

As far as I know, the planetary plane does not change in regards to the sun it orbits, which would make for a slightly better reference in the long run than the planetary equator.