IFOV
Instantaneous field of view.

IFSAR
InterFerometric Synthetic Aperture Radar

IHS
Intensity, hue, and saturation system of colors.

Image
pictorial representation of a scene recorded by a remote sensing system. Although image is a general term, it is commonly restricted to representations acquired by non-photographic methods.

Image dissection
The breaking down of a continuous scene into discrete spatial elements, either by the receptors on the retina, or in the process of capturing the image artificially.

Image striping
A defect produced in line scanner and pushbroom imaging devices produced by the non-uniform response of a single detector, or amongst a bank of detectors. In a line-scan image the stripes are perpendicular to flight direction, but parallel to it in a pushbroom image.

Image swath
See ground swath.

IMU
Inertial Measuring Unit. Laser gyro equipment able to measure aircraft’s absolute position in space.

Incidence angle
In radar, the angle formed between an imaginary line normal to the surface and another connecting
the antenna and the target.

Incident energy
Electromagnetic radiation impinging on a surface.

Index of refraction (n)
Ratio of the wavelength or velocity of electromagnetic radiation in a vacuum to that in a substance.

Instantaneous field of view (IV)
Solid angle through which a detector is sensitive to radiation. In a scanning system, the solid
angle subtended by the detector when the scanning motion is stopped.

Intensity
In the IHS system, brightness ranging from black to white.

Interactive processing
Method of image processing in which the operator views preliminary results and can alter
the instructions to the computer to achieve desired results.

Interpretation
The process in which a person extracts information from an image.

Interpretation key
Characteristic or combination of characteristics that enable an interpreter to identify an object on an image.

IR
Infrared region of the electromagnetic spectrum that includes wavelengths from 0.7µm to 1 mm.

IR color photograph
Color photograph in which the red-imaging layer is sensitive to photographic IR wavelengths, the green-imaging layer is sensitive to red light, and the blue-imaging layer is sensitive to green light. Also known as camouflage detection photographs and false-color photographs.

ISO index
Index of the International Standards Organization, designating film speed in photography.
Higher values indicate higher sensitivity.

Isotherm
Contour line connecting points of equal temperature. Isotherm maps are used to portray surface-temperature patterns of water bodies.