Thanks, Jim.
Working off your observation, I opened a new drawing, and as you said, the attribute dictionary "Georeference" is empty. All the default geodata is in the shadow_info object (or hash, I'm not sure of the proper term). I listed it like this:
am = Sketchup.active_model
#<Sketchup;;Model;0x63be010>
am.shadow_info.each{|k,v| puts "#{k} #{v}"}
City Boulder (CO)
Country USA
Dark 45
DayOfYear 312
DaylightSavings false
DisplayNorth false
DisplayOnAllFaces true
DisplayOnGroundPlane true
DisplayShadows false
EdgesCastShadows false
Latitude 40.017
Light 80
Longitude -105.283
NorthAngle 0.0
ShadowTime Fri Nov 08 07;30;00 Central Standard Time 2002
ShadowTime_time_t 1036762200
SunDirection (-0.423824071310226, -0.772439983723215, 0.472979521886207)
SunRise Fri Nov 08 00;43;14 Central Standard Time 2002
SunRise_time_t 1036737794
SunSet Fri Nov 08 10;46;34 Central Standard Time 2002
SunSet_time_t 1036773994
TZOffset -7.0
UseSunForAllShading false
nil
Checking the "Use Georeference" box creates the attribute dictionary and probably uses the shadow_info coordinates to set the lat and long.
I want to programatically check the "Use Georeference" box on a batch of files. I can't assume it exists so I'll need to create the attribute dictionary "Georeference" exactly. I suppose I should make the shadow lat/long and the georeference lat/long match to avoid future confusion.
I this the way to go?