radalt v pressure alt
dClbydalpha,
I have been looking at graphs of descent, comparing the radalt with calculated True Alt. While True alt shows a very steady decline, the radalt shows some irregularity. From what you are saying it appears that this may be caused, not by excessive speed, but by irregularity on the ground confusing the return signal. It seems reasonable that the likelihood of confusion would be greater at high speed, and also greater at high altitude where the footprint of the signal would be wider.
Would it be right therefore to conclude that radalt would be highly accurate at low altitude over relatively smooth terrain no matter how high the ground speed?
Do you have any information about the angle of the cone of the signal, so that it would be possible to calculate from the height how far off line an object like a building might be picked up and interfere?