[Captain Joy]

Originally Posted by Agemegos

What outputs should I display?

The 4th ed. Planetary Record Sheet displays the following: Planet #, Name, Orbital Radius, Type, Diameter, Density, Gravity, Atmosphere, and Notes all on one row for each planet in a system. You might start with that just to be consistent with SJGames. You could then add other options. E.g. my spreadsheet gives the Star Trek class of the planet--Earth is M class.

Originally Posted by Agemegos

What about eccentricity?

I'd mention it in the "Notes" column if it's more than 0.1.

Originally Posted by Agemegos

World type is essential.

Agreed. I'm surprised this isn't in the official 4th ed. Planetary Record Sheet, but "Density" is. (Agreed, get rid of "Density".)

Originally Posted by Agemegos

World diameter is essential, and Earth diameters are more useful than kilometres or miles.

More useful, but not cooler. Use miles or km. (You and you players will have Earth's diameter memorized in no time and will enjoy looking at a Galactic Survey Report that has real life units and understand what they're looking at.

Originally Posted by Agemegos

Atmospheric composition class is essential, as is either the pressure in bars or the pressure category but not both.

Agreed. The trick is including this and still have all the data fit on one row. I opted for listing the primary constituents and the pressure category. E.g. N2, CO2, dense.

Originally Posted by Agemegos

Hydrographic percentage and composition are essential.

I think you'll find they're not. Most planets will have 0%. Any planet that isn't 0% will likely be interesting enough to have it's own record sheet and you can provide that information there. In practice, most systems will have only one (if that) planet worthy of a proper Planetary Record Sheet. In my game, a typical Galactic Survey Report gives all the info for the most habitable planet (which would include Hydrographic coverage) and then the row-by-row list of info for all the other bodies in the system (which usually all have 0% Hydrographic percentage anyway).

Originally Posted by Agemegos

Surface temperature is essential but black-body temperature is quite unimportant. I don't think we need climate type if we list temperature.

It's not on the 4th ed. Planetary Record Sheet; but I agree, and it's something I added to my read-outs.

Originally Posted by Agemegos

Tidal locking? I'm tempted to note this on the system table.

I know you're aware, the errata for GURPS: Space is woefully incomplete. Others who are reading this thread should be aware of a better list of GURPS: Space errata

Originally Posted by Agemegos

Habitabilty belongs on the system table. RVM and Affinity I'm not sure about.

Since these are simple numbers, you might adopt a convention like H(R,A)

Originally Posted by Agemegos

Axial tilt?

You might include it in a "Notes" column for any Axial Tilt greater than 45%.

Originally Posted by Agemegos

I can effectively colour-code four categories.

Ah, I love colour-coding.

If you want my conditions for converting GURPS stats to Star Trek (actually, PRIME DIRECTIVE) planetary classes, let me know. (It will take me a few weeks to get them to you as I'm on holiday right now.)