EM 1110-2-2907
1 October 2003
Periodic line striping
Defect on Landsat MSS or TM images in which every sixth or sixteenth
scan line is brighter or darker than the others. Caused by the sensitivity
of one detector being higher or lower than the others.
Photodetector
Device for measuring energy in the visible-light band.
Photogeology
Mapping and interpretation of geologic features from aerial
photographs.
Photograph-
Representation of targets on film that results from the action of light on
silver halide grains in the film's emulsion.
Photographic IR
Short-wavelength portion (0.7 to 0.9 m) of the IR band that is
detectable by IR color film or IR black-and-white film.
Photographic UV
Long-wavelength portion of the UV band (0.3 to 0.4 m) that is
transmitted through the atmosphere and is detectable by film.
Photomosaic
Mosaic composed of photographs.
Photon
Minimum discrete quantity of radiant energy.
Photopic vision
Vision under conditions of bright illumination.
Picture element
In a digitized image, the area on the ground represented by each digital
number. Commonly contracted to pixel.
Pitch
Rotation of an aircraft about the horizontal axis normal to its longitudinal
axis that causes a nose-up or nose-down attitude.
Pixel
Contraction of picture element.
Planck's Law
An expression for the variation of emittance of a blackbody at a
particular temperature as a function of wavelength.
Point spread function
The image of a point source of radiation, such as a star, collected by an
(PSF)
imaging device. A measure of the spatial fidelity of the device.
The direction of orientation in which the electrical field vector of
electromagnetic radiation vibrates.
Polar orbit
An orbit that passes close to the poles, thereby enabling a satellite to
pass over most of the surface, except the immediate vicinity of the
poles themselves.
Polarized radiation
Electromagnetic radiation in which the electrical field vector is
contained in a single plane, instead of having random orientation
relative to the propagation vector. Most commonly refers to radar
images.
Positive photograph
Photographic image in which the tomes are directly proportional to the
terrain brightness.
Precision
Precision is a statistical measurement of repeatability that is usually
expressed as a variance or standard deviation, root mean square or
RMS, of repeated measurements. These are expressed as x, y
coordinates of arcs, label points, and tics in either single or double
precision in ARC/INFO.
Single-precision coordinates have up to seven significant digits of
precision. This allows for a level of accuracy of approximately 10
meters for a region whose extent is 1,000,000 meters across. Double-
precision coordinates have up to 15 significant digits; this allows for the
precision necessary to represent any desired map accuracy at a global
scale.
Previsual symptom
A vegetation anomaly that is recognizable on IR film before it is visible
to the naked eye or on normal color photographs. It results when
stressed vegetation loses its ability to reflect photographic IR energy
and is recognizable on IR color film by a decrease in brightness of the
red hues.
Primary colors
A set of three colors that in various combinations will produce the full
range of colors in the visible spectrum. There are two sets of primary
colors, additive and subtractive.
Principal component
The analysis of covariance in a multiple data set so that the data can be
analysis
projected as additive combinations on to new axes, which express
different kinds of correlation among the data.
Glossary-22
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