Target Height Estimation using Multipath Over Land

Airborne radars often receive more than one report on airborne targets due to what is called multipath. Multipath is merely a second, and sometimes third, radar report at a greater range than the actual target. The multipath reports are due to reflections from the earth, and if the location and altitude of the point of reflection is known, the altitude of the target can usually be estimated with good accuracy. This concept is nothing new, and it is believed it may already be employed for operation over water by other systems. The Airborne Warning and Control System (AWACS) radar has never utilized multipath for height finding because it operates a substantial part of the time over land, and no algorithms for multipath height finding over land were available. More recently, availability of Digital Terrain Elevation Data (DTED) and improvements to the AWACS radar have prompted an investigation into the possibility of adding this capability. The result of this work, we believe, is the first known solution for using multipath radar reports over land to determine target altitude.