L band: Radar bandwidth from 0.39-1.55 GHz (150-300 mm).
Le: Standard symbol for radiance.
Lv: Standard symbol for luminance.
LAC: Local Area Coverage; standard recording
mode for AVHRR to give 1.1 km pixel image.
LAI: Leaf Area Index.
Lambertian surface: An ideal, perfectly diffusing surface, which
reflects energy equally in all directions.
Landcover: Landcover generally refers to actual ground cover, eg,
vegetation, crops, urban areas and open water. It also includes associations
of the Earth's surface and its cover, such as forests, which are composites
of various covers. The term reef zone is often used in reef mapping in place
of land cover.
Landcover class: A specially defined grouping which contains pixels
from an image that belongs to the same surface and surface cover association
(see land cover).
Land use: The current use of an area of land. This term is different
to, but often confused with, land cover.
Landform: Shape, form and nature of the Earth's surface.
Landsat: An unmanned, earth-orbiting series of satellites, initiated
by the National Aeronautic and Space Administration (now managed by EOSAT),
that transmit images to earth receiving stations. These satellites were
designed primarily for collection of earth resources data. The current Landsat
satellites contains the seven channel thematic mapper (TM) multi-spectral
system. The first satellite Landsat 1 (originally called ERTS: Earth Resources
Technology Satellite) was launched June 1972.
Landsat MSS: An electromechanical multi-spectral scanner carried
on all five of the Landsat satellites which records four channels of electromagnetic
radiation: 500-600 nm, 600-700 nm, 700-800 nm and 800-1100 nm for an optical
pixel size of approximately 80 m.
Landsat TM: An electromechanical multi-spectral scanner carried on
the Landsat 4 and 5 satellites which records seven channels of electromagnetic
radiation: 450-520 nm, 520-600 nm, 630-690 nm, 769-900 nm, 1.55-1.75µm
and 2.08-2.35 µm for an optical pixel size of 30 m and 10.4-12.6 µm
for an optical pixel size of 120 m.
Laplacian: (1) A filter in which the central value is subtracted
from the average of its neighbourhood. The operation enhances edges and
its name refers to its identity as a discrete form of the Laplacian derivative.
Large scale: (1) Aerial photography with a representative fraction
of 1:500 to 1:10,000. (2) Maps with a representative fraction (scale) greater
than 1:100,000.
Laser: Light Amplification by Stimulated Emission of Radiation. A
device for producing light by emission of energy stored in a molecular or
atomic system when stimulated by an input signal.
Laser Airborne Depth Sounder (LADS): Active remote sensing system
developed by Australian defence research laboratories for shallow water
mapping.
Lidar: Light Detection and Ranging; active remote sensing system
using visible wavelengths of the EM spectrum.
Light: Visible radiation (about 0.4-0.7 µm in wavelength) considered
in terms of its luminous efficiency, that is, evaluated by its ability to
stimulate the human sensation of sight.
Light pen: A pointer-like device, used in conjunction with a display
screen, that provides a signal to identify particular elements displayed
on the screen for later reference.
Lightness: Brightness of an area judged relative to the brightness
of a white or highly-transmitting object/colour which has similar illumination.
Lineament: A linear topographical or tonal feature on the terrain
and on images and maps, which may represent a zone of structural weakness.
Linear feature: A linear pattern or alignment of discontinuous patterns
evident in an image, photograph, or map, which represents some degree of
linearity of a single, or diverse grouping of, natural or cultural ground
feature(s).
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.
lm: Abbreviation for lumen.
Look-up table (LUT): A conversion table used to convert data in one
distribution to another distribution.
Low-pass filter: A spatial-frequency filter which suppresses the
high-frequency contrast variations in an image, and enhances the broad variations.
LTM: Local Transverse Mercator. This projection defines a non-standard
UTM zone centred at the centre of a remotely sensed image.
lumen (lm): SI unit for luminous flux.
Luminance (Lv): Photometric measure of the radiant intensity of a
light source. SI units are 1m sr-1 m-2 or cd m-2. Radiometric equivalent
is radiance.
Luminosity: Luminance scale corrected for the human eye's perception
of brightness.
Luminous energy (Qv): Quantity of light. Standard measurement unit
lm sec.
Luminous flux (Fv): Luminous energy per unit time. Standard measurement
unit lm.
Luminous intensity (Iv): Luminous energy per solid angle of measurement.
Standard measurement unit is lm sr^-1 or Cd.
LUT: Look-Up Table.