Fields and Radiation

Definition

Remote sensing is the technique to retrieve information about an object without being in physical contact with it (Elachi, 1987). This information is acquired by detecting and measuring changes that the object under investigation imposes on the surrounding field.

The interacting field can be an electromagnetic, acoustic, or gravitational field. The electromagnetic field is due to space–time variations of the electric and the magnetic fields (Ulaby et al., 1981; Ishimaru, 1991). Static electric and magnetic fields can be originated by a stationary electric charge distribution or by stationary currents or ferromagnetic materials, respectively. The electromagnetic methods, which are the most frequently used in remote sensing, cover the whole electromagnetic spectrum from radio-frequency waves to gamma rays through microwaves, submillimeter waves, and far infrared, near infrared, visible, ultraviolet, and x-ray waves. Acoustic fieldsare due to the continuous exchange between...