Ted wrote:
And then, they build that nice new 2,000 ft radio tower....

This brings up an interesting idea of putting an electronic beacon on new
structures for the first year or so until all terrain data bases get
updated.

That's basically an idea we submitted to the FAA many years ago, back
before ADS-B was called ADS-B. In addition to the usual
"squirt/listen" in each aircraft, add a simple squirter to each tower
above a certain AGL height (same as the "flashing red light" rules).
Nothing special required to the aircraft installation - the antennas
and other such obstacles simply look like aircraft to avoid.

Total cost (we were talking about low power VHS) of the transmitter in
todays dollars would be around $15 per tower (less any FAA
administration fees and liability insurance). Even that is probably a
high figure - more for the weatherized case than anything else. Since
the obstacles presumably never moves, no GPS required - just a fixed
string msg.

[Oh yeah, the then administrator nixed the idea. Said in-cockpit
weather and aircraft imagery was too complicated for pilots to
understand, and that the only thing he would EVER approve was the
uplink of text weather and charts.]