Three things

[rasqual]

1. Great circle for army travel. The lack of polar crossings for short distances is appalling, simply appalling. ;-)

2. Cost for everything that should cost. Moving armies. Billeting armies. And so forth.

3. Most important: Use real-world data. It doesn't even matter what it is -- get your feet wet. The Earthquake instance from USGS is good not necessarily because it would be something awesome for the game, but because the source is reputable and reliable -- a lot like a layer. Not some fly-by-night feller with a network link that could go down any day and leave you high and dry.

If I had to choose which of these to emphasize, I'd say item 3. Seriously. I think once you get your feet wet, you'll find yourself desperate to use even more real-world data. Fires, Storms, Precipitation, Drought -- anything from a reliable, authoritative source.

It might be worth doing some simulation where real-world data isn't available. However, anything involving lat/lon needs to be compensated for latitude. The polygons are just one example of how this currently isn't in play (look at dude in Antarctica, trying to hide by having a skinny polygon) LOL

Perhaps using UTM might be an answer to some of all this trouble . . .

More formulae:

http://williams.best.vwh.net/avform.htm
http://www.uwgb.edu/dutchs/UsefulData/UTMFormulas.HTM
http://www.gpsy.com/gpsinfo/geotoutm/