GPS

I would think by 2183, based on some current 
satellite sizes, a GPS constellation which would 
offer decent coverage to most of the planet for 
a period of months to a year could be 
deployed using semi-disposable satellites that 
are about the size of a small desk with their 
antennae arrays folded (or motorcycle). You'd 
probably need between 24 and 70 of them. I'd 
expect a ship with an experienced crew and 
shuttles to lay these could have these up and 
running within 2-7 days. This requires localized 
space superiority to do practically. Because you 
can also use the tactic of deploying 700 even 
smaller satellites and therefore can stand losing 
a fair number before service is significantly 
degraded (this is something that has been 
considered in several areas of satellite service), 
it is possible to construct (in theory) a cheap 
network with high redudancy. 

If a major invasion was planned, as soon as 
effective local space supremacy was achieved a 
modified freighter (fleet auxilliary) would deploy 
multiple cargo shuttles each carrying 5 ot 6 of 
these sattelites and I'd imagine they could be 
placed fairly rapidly (say 1 every 4-6 hours). 
With the smaller satellites, you'd deploy more of 
them faster as you don't need to move as far 
between deployments. With good auto-
deployment systems, this should also be a fast 
process. 

Now, GPS will only tell you where on the globe 
you are. To add all the terrain mapping, etc 
may require some larger satellites to be in 
place, but I'd assume most Core, Inner and 
even significant outer colonies would be surface 
mapped to 1m or less accuracy. I'd assume 
smaller outer colonies, outposts and whatnot 
would often have only the mapping done by 
survey ships and extra information about the 
landing/settlement sites, so their would be 
more work to be done if one wanted to use 
terrain data in outlying areas (giving the locals 
a region to retreat to that the enemy wouldn't 
have good data about). 

But, that's all IMU. :)

T. 
---------------------------------------------
Thomas Barclay
Co-Creator of http://www.stargrunt.ca 
Stargrunt II and Dirtside II game site

No Battle Plan Survives Contact With Dice.
-- Mark 'Indy' Kochte