Thanks. We really like it, too.
A 30' diameter x 5' tall dome will have a 25' radius of curvature. That's a 50' diameter sphere. Or look at the dome as being 15' radius. It's a really big sphere (almost twice as large as the dome diameter).
The answers are in the value you input. If you say 30 x 15 it could mean inches, millimeters, feet, meters, miles, light years -- it doesn't care. So the output units are the same as the input units.