AVweb responds ...
Thanks for writing. While your idea may have merit for some locations, I don't think it can replace space-based GPS for wide-area navigation. The problem is that ground stations are subject to range limitations due to the horizon, which affects low-altitude airplanes and, of course, all ground vehicles. I think that's why the military is working on the airborne "pseudolite" concept as a way to overcome jamming over a wider area -- and being based on an aircraft (manned or unmanned) will make it possible to deploy pseudolites anywhere they're needed. (Adobe Acrobat PDF on pseudolites available here.)
This is a companion discussion topic for the original entry at https://www.avweb.com/features/reader-mail/avmail-february-20-2003