In article ,
Derek Lyons wrote:
...you need to invest substantial resources to build a GPS equivalent at,
say, Mars.

Do you really need a GPS analog? It seems a couple of beacons that
could act as a pseudo-Transit would be Really Handy - and much cheaper
and easier than a GPS type system.

I'm not sure how well that would work for certain important cases like
navigating incoming spacecraft; I'd have to think about it for a while.
The Transit scheme is at its best when the navsat is passing fairly near
the observer at fairly high relative velocity, e.g. a LEO pass over a
ground observer on Earth.

Might help enough to be worth doing even if it didn't provide a complete
navigation solution, mind you.
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