I was chatting online with some non-pilots who knew I was a pilot and one, whom I have dubbed Rhubarb, asked me, "Why doesn't each airport have a local positioning signal?" They kind of do, so I asked what he meant.
<Aviatrix> What is a local positioning signal?
<Aviatrix> A lot of them have a green and white flashing beacon, if that counts.
<Rhubarb> Well, like GPS, but local.
<Rhubarb> A collection of transmitters whose signals can be recieved and processed the same way.
<Aviatrix> A lot of them also have an AM radio broadcast signal in morse code from quite nearby. You can't put it ON the runway because the antenna would be inconvenient.
<Aviatrix> Some have a transmission in the range 108-117.9 MHz with directional information that helps you align with the runway.
<Rhubarb> What I'm proposing would undoubtedly involve a whole 'nother receiver, and I guess adding more instruments is not an easy proposition. :-P
<Aviatrix> And some even have information in that signal that tells you how far away the runway is, and/or your deviation from an ideal glideslope to the runway.
Rhubarb kind of answered his own question, by recognizing that every technology needs a receiver, before I got into historical techniques like A-N beacons, painting the name of the airport in big letters, or lighting bonfires leading to the airport. A local positioning signal is a very good idea, and has been implemented in many ways. Maybe when I'm in a researchy mood I'll enumerate the dates and instigators of all the various local positioning signals that have been used over the last hundred years.
If another blogger wants to steal that idea, and backlink it here for the traffic, it's yours for the taking.