Harmonic
Refers to waves in which the component frequencies are whole- number multiples
of the fundamental frequency.

Heat capacity (C)
Ratio of heat absorbed or released by a material to the corresponding temperature rise or fall. Expressed in calories per gram per degree centigrade. Also called thermal capacity.

Heat Capacity Mapping Mission (HCMM)
NASA satellite orbited in 1978 to record daytime and nighttime visible and thermal
IR images of large areas.

Highlights
Areas of bright tone on an image.

High-Pass filter
A spatial filter which selectively enhances contrast variations with high spatial frequencies in an image.
It improves the sharpness of images and is a method of edge enhancement.

HIRIS
High Resolution Imaging Spectrometer, possibly to be carried by the Space Shuttle.

HIRS
High Resolution Infrared Spectrometer, carried by NOAA satellites.

Histogram
A means of expressing the frequency of occurrence of values in a data set within a series of equal ranges or bins, the height of each bin representing the frequency at which values in the data set fall within the chosen range. A cumulative histogram expresses the frequency of all values falling within a bin and lower in the range. A smooth curve derived mathematically from a histogram is termed the probability density function (PDF).

Homologous Point
Pair of pixels representing the same point in two stereoscopic images.

Hue
In the IHS system, represents the dominant wavelength of a color.