What is the difference between slant range and ground range?
The SAR sensor emits first a single pulse of microwave energy, then waits for the returns from the ground. Energy reflected from objects closer to the satellite (in the satellite-Earth direction) will come back to the sensor before energy reflected from objects further away. A certain delay in the return of the signal corresponds to a certain distance from the satellite. The receiver onboard the platform samples the returned signal at high frequency. The time delay between a signal and the following will correspond to a certain relative distance between the two points from which the signals originate. This distance is along the direction the spacecraft is looking. The highest the frequency with which the receiver samples the returns, the highest the resolution in distance between two close points. As the following image (from http://www.asf.alaska.edu/7_4_2_12.html) shows, this resolution is called slant range resolution and is about 8 meters for ERS. The slant range resolution project
