> The use of primary radar requires a great deal of signal power, because objects further from the antenna will reflect or send back a weak signal. At longer distances from the antenna, radar becomes unreliable as a way to determine aircraft position with only reflected signals.
Radar derives altitude from measurements of distance and elevation angle. The greater the distance, the less sensitive elevation angle is to vertical displacement (simple trigonometry), and hence signal:error decreases.
If the last effect on the page were in effect, you might get a return, know it's relative bearing well, it's range a little less well, and it's altitude not very well at all.
