EM 1110-2-2907
1 October 2003
Latent image
Invisible image produced by the photochemical effect of light on silver
halide grains in the emulsion of film. The latent image is not visible until
after photographic development.
Layover
In radar images, the geometric displacement of the objects toward the
near range relative to their base.
L band
Radar wavelength region from 15 to 30 cm.
Lens
One or more pieces of glass or other transparent material shaped to
form an image by refraction of light.
LEVEL 1b
Level 1b is considered raw quality controlled data configured into
discrete data sets and to which Earth location and calibration
information have been appended, but not applied.
LFC
Large-format camera. The LFC was a high altitude aerial mapping
camera scaled up to operate from the Space Shuttle in Earth-orbital
altitudes. LFC specifications included:
Film Format Size: 9 x 18 inches (23 x 46 cm)
Lens Aperture: F/6.0 -Lens Focal Length: 12 inches (30.5 cm)
Exposure Interval: 7.5 sec.
Exposure Range: 1/250 to 1/31.25 seconds
Ground Resolution: 20 meters at 160 nautical miles
Ground Coverage: 120 x 240 nautical miles at 160 nm
LIDAR
Light intensity detection and ranging, which uses lasers to stimulate
fluorescence in various compounds and to measure distances to
reflecting surfaces.
Light
Electromagnetic radiation ranging from 0.4 to 0.7m in wavelength that
is detectable by the human eye.
Light meter
Device for measuring the intensity of visible radiation and determining
the appropriate exposure of photographic film in a camera.
Lineament
Linear topographic or tonal feature on the terrain and on images, maps,
and photographs that may represent a zone of structural weakness.
Linear
Adjective that describes the straight line-like nature of features on the
terrain or on images and photographs.
Lineation
The one-dimensional alignment of internal components of a rock that
cannot be depicted as an individual feature on a map.
Line drop out
The loss of data from a scan line caused by malfunction of one of the
detectors in a line scanner.
Line-pair
Pair of light and dark bars of equal widths. The number of such line-
pairs aligned side by side that can be distinguished per unit distance
expresses the resolving power of an imaging system.
Line scanner
An imaging device, which uses a mirror to sweep the ground surface
normal to the flight path of the platform. An image is built up as a strip
comprising lines of data.
Look angle
The angle between the vertical plane containing a radar antenna and
the direction of radar propagation. Complementary to the depression
angle.
Look direction
Direction in which pulses of microwave energy are transmitted by a
radar system. The look direction is normal to the azimuth direction. Also
called range direction.
Look-up table (LUT)
A mathematical formula used to convert one distribution of data to
another, most conveniently remembered as a conversion graph.
Longitude
The angular distance from the Greenwich meridian (0 degree), along
the equator. This can be measured either east or west to the 180th
meridian (180 degrees) or 0 degree to 360 degrees W.
Low-sun-angle
Aerial photograph acquired in the morning, evening, or winter when the
photograph
sun is at a low elevation above the horizon.
Glossary-18
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