Stan Gosnell wrote:
AFAIK the GPS approach uses the end of the runway for the approach point.
The reason an ILS takes you further down is that the GS transmitter is
located down the runway, not at the end. With a GPS, any position can be
used, unlike an ILS where the transmitters have to be placed down the way,
not at the end of the runway because of obstruction and interference reasons.

I suspect that's not the only reason. Putting the CS 1000 feet down
the runway gives you 50 feet (the height of an FAA-standard tree!)
threshold crossing height. This is convenient to have when your GS
receiving antenna is mounted at a higher elevation than your wheels.
Or is that the "obstruction" reason you mention?

If you follow a synthetic GPS "glide slope" which starts at the
threshold all the way to the ground, your GPS antenna will clear the
approach lights but your wheels won't.