Originally Posted by
vapilot2004
Military radar surveillance systems, whether ground-based or airborne can easily determine the altitude of a target without mode C data or with no transponder signal at all.
Typical is a 3D system where 2 antennas handle the azimuth and bearing detection individually. The bearing/distance antenna axis is horizontal and the azimuth antenna axis is vertical.
The newest digital 3D systems can detect a target's azimuth position by ramping the pulse frequencies and correlating small changes in the returning beam angle which can then be used to compute altitude. Only one antenna rotating in the horizontal plane is needed.
Fine. But can you deduce
pressure altitude to within 300 feet with such a system?