Detection vs. Transponding

Hi there,

I'd like to use computer control on my outdoor layout with digitrax.  Can I do that with transponding alone?  

If transponding not only tells whether something is on the track but also what is there, then why use detection at all?

I'd like to locate all the equipment in a building (1:1 scale) that is centrally located, but it will be several hundred feet from the exteme ends of the railroad.  I understand feeder length doesn't matter with transponding.  Is it true I can have reliable transponding even with feeders that are a few hundred feet long?

TIA,
Josh