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Earth Imaging Glossary
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" L "
LAC--Local Area Coverage
LAC are full resolution data that are recorded on an onboard tape recorder for subsequent
transmission during a station overpass. The average instantaneous field-of-view of 1.4
milliradians yields a LAC ground resolution of approximately 1.1 km at the satellite nadir
from the nominal orbit altitude of 833 km (517 mi).
LAMBERT AZIMUTHAL EQUAL AREA PROJECTION
Azimuthal projections are formed onto a plane which is usually tangent to the globe at either
pole, the Equator, or any intermediate point. The Lambert Azimuthal Equal Area projection
is a method of projecting maps on which the azimuth or direction from a given central point
to any other point is shown correctly and also on which the areas of all regions are shown in
the same proportion of their true areas. When a pole is the central point, all meridians are
spaced at their true angles and are straight radii of concentric circles that represent the
parallels.
This projection is frequently used in one of three aspects: The polar aspect is used in atlases
for maps of polar regions and of the Northern and Southern Hemispheres; the equatorial
aspect is commonly used for atlas maps of the Eastern and Western Hemispheres; and the
oblique aspect is used for atlas maps of continents and oceans.
LAMBERT CONFORMAL CONIC PROJECTION
The Lambert Conformal Conic Projection is derived by the projection of lines from the
center of the globe onto a simple cone. This cone intersects the Earth along two standard
parallels of latitude, both of which are on the same side of the equator. All meridians are
converging straight lines that meet at a common point beyond the limits of the map. Parallels
are concentric circles whose center is at the intersection point of the meridians. Parallels and
meridians cross at right angles, an essential of conformality.
To minimize and distribute scale errors, the two standard parallels are chosen to enclose two-
thirds of the north to south map area. Between these parallels, the scale will be too small, and
beyond them, too large. If the north to south extent of the mapping is limited, maximum scale
errors will rarely exceed one percent. Area exaggeration between and near the standard
parallels, is very slight; thus, the projection provides good directional and shape relationships
for areas having their long axes running in an east to west belt.
LANDSAT (formerly ERTS)
The Landsat program, first known as the Earth Resources Technology Satellite (ERTS)
Program, is a development of the National Aeronautics and Space Administration (NASA) in
association with NOAA, USGS, and the Space Imaging. The activities of these combined
groups led to the concept of dedicated Earth-orbiting satellites, the defining of spectral and
spatial requirements for their instruments, and the fostering of research to determine the best
means of extracting and using information from the data. The first satellite, ERTS 1, was
launched on 7/23/72. The second satellite was launched on 1/22/75. Concurrently the name
of the satellites and program was changed to emphasize its prime area of interest (land
resources). The first two satellites were designated as Landsats 1 and 2. Landsat 3 was
launched on 3/5/78. Landsat 4 was launched on 7/16/82. Landsat 5 (launched 3/1/84) is
currently in service providing selected data to worldwide researchers.
LAS--Land Analysis System
The LAS is an image analysis system designed to ingest, manipulate, and analyze digital
image data by providing the user with a wide array of functions and statistical tools. LAS
supports research and production for remote sensing, image processing, and geographic
information systems (GIS). It provides a flexible framework for the processing and the
analysis of image data as well as for algorithm development. It is the main software system
for the production image processing capabilities at the U.S. Geological Survey's EROS Data
Center (EDC).
LAS HEADER
A LAS image header contains descriptive information about an image file. This header is
located in the first 512-byte record of the image file. This information record is mandatory
for all LAS images accessed directly from computer or optical disk.
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 n.m.
LINHOF AERO TECHNIKA CAMERAS
NASA has modified the Linhof cameras to operate in zero gravity on board the Space
Shuttle. The camera utilizes a five-inch film format and is equipped with interchangeable
lenses (90 mm and 250 mm). A data recording module (DRM) is also mounted on the camera
to record the date, time (Greenwich Mean Time), mission number, roll number, and frame
number for each photograph. The Linhof camera is used to acquire earth-looking
photography through four viewing ports on board the Shuttle.
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Glossary Home
Initial content for this Glossary of terms has been graciously supplied by RADARSAT International - www.rsi.ca
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