Hardcopy: Printed or plotted computer output in a visually readable
form.
Hardware: The physical components of a computer and its peripheral
equipment. Contrasts with software.
Hemispherical reflectance: Radiant flux measured over a hemispherical;
sometimes called bihemispherical reflectance.
Hertz (Hz): Standard unit for frequency.
High-pass filter: A spatial filter which selectively enhances contrast
variations with high spatial frequencies in an image. It improves the sharpness
of the images, and is a method of edge enhancement.
Histogram: A way 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.
Homogeneous pixel: When a pixel falls within one land cover type
on the ground it is called a homogeneous pixel.
Hotspot: The destruction of fine image detail on a portion of a wide-angle
aerial photograph. It is caused by the absence of shadows and by halation
near the prolongation of a line from the sun through the exposure station.
HRV: High Resolution Visible scanner; carried on SPOT satellite.
HTML: Hypertext Markup Language. The authoring language used to
produce world wide web documents.
Hue: That attribute of a colour by virtue of which it differs from
grey of the same brilliance, and which allows it to be classed as red, yellow,
green, blue, or intermediate shades of these colours.
Hz: Abbreviation for hertz.