Patent ID: 6204800
Filing Date: 2001-03-20
Classification: G01S

Abstract:
A method for monitoring the earth's surface by using an aircraft having a synthetic aperture radar sensor, comprising the steps of:(a) using a transmitting/receiving antenna of the radar sensor to illuminate a spot in a region to be monitored, the illuminated spot having a predetermined spatial resolution;(b) receiving, radar signals via the transmitting/receiving antenna;(c) generating a radar image from the received radar signals through superimposing Fourier spectra, which succeed each other in time and which have been processed block-by-block with respect to a range parameter and a Doppler parameter;(d) determining acceleration on a line of sight (B.sub.los) between the illuminated spot and the transmitting/receiving antenna, as well as ambiguity errors on the line of sight (M.sub.los), step (d) including correlating the Fourier spectra in an azimuth dimension and an elevation dimension;(e) determining a speed component on the line of sight (R.sub.los) within an ambiguity range by estimating an echo center of gravity of the Doppler parameter within the Fourier spectra;(f) determining a definite speed on the line of sight (V.sub.los) in accordance with the following formula:(V.sub.los)=M.sub.los).multidot..lambda.B.sub.m /2+R.sub.los,wherein.multidot.=multiplication operator.lambda.=radar wave length; andB.sub.m =measuring band width of the radar sensor in Doppler; and(g) determining a phase correction ""range"" parameter (.phi..sub.r) and a phase correction Doppler parameter (.phi..sub.d), which are necessary for focusing radar images, from the acceleration on the line of sight (B.sub.los) and the speed on the line of sight (V.sub.los).