Background: Any effect in a sensor or other apparatus or system,
above which the phenomenon of interest must manifest itself before it can
be observed.
Backscatter: The scattering of radiant energy into the hemisphere
of space bounded by a plane normal to the direction of the incident radiation
and lying on the same side as the incident ray; also called backscattering.
Band: (1) A selection of wavelengths. (2) Frequency band. (3) Absorption-band.
(4) A group of tracks on a magnetic drum. (5) A range of radar frequencies,
such as X or Q band.
Bandwidth: (1) In an antenna, the range of frequencies within which
its performance, with respect to some characteristic, conforms to a specified
standard. (2) In a wave, the least frequency interval outside which the
power spectrum of a time-varying quantity is everywhere less than some specified
fraction of its value at a reference frequency. (3) The number of cycles
per second between the limits of a frequency band.
Base map: A map upon which information may be placed for comparison
or geographical correlation.
Batch processing: A computer processing system in which the entire
processing operation is pre-defined by a job request then conducted without
further instruction. Contrasts with interactive processing.
Beam: A focused pulse of energy.
Bidirectional reflectance: Reflectance measurement where angles of
incidence and collection are directional (eg, satellite sensor measurements
on a sunny day).
Bidirectional reflectance distribution function (BRDF): Bidirectional
reflectance at all possible angles of collection. This is difficult to measure
so is frequently simplified to the bidirectional reflectance factor.
Bidirectional reflectance factor (BRF): Ratio between the spectral
radiance at an angle to the object of interest and the spectral radiance
of a diffuse reflector at the same angle within the scene.
Bihemispherical reflectance: Reflectance measurements where angles
of incidence and collection are measured over a hemisphere (eg, most laboratory-based
measurements).
BIL: Band Interleaved by Line. Multi-channel image format where data
is recorded by a channel for each line, that is:
record 1: line 1 in channel 1
record 2: line 1 in channel 2
record n: line 1 in channel n
record n + 1: line 2 in channel 1
...
record n x m: line m in channel n
for m lines and n channels in the image.
Bilinear interpolation: A resampling technique which considers
the image neighbourhood values of a location in determining its output pixel
value.
Bin: One of a series of equal intervals in a range of data. This
term is commonly used to describe the divisions in a histogram.
Binary: A numerical system using the base 2. This system represents
all other numbers using the two digits 0 and 1. Each digit of a binary number
represents a power of 2, eg:
2^0 = 1 in binary system (1 in decimal system)
2^1 = 10 in binary system (2 in decimal system)
2^2 = 100 in binary system (4 in decimal system)
Binary digit: A single digit in the binary number system, 0 or 1.
Binary numbers are well suited for use by electronic devices, such as computers,
as they can be represented by two distinct states, on and off.
Biomass: Amount of chemical energy contained in a group of growing
plants at any given time; expressed as grams of dry matter per square metre.
This differs from yield which is the amount of energy stored in the desired
fruit or grain.
Bit: (1) An abbreviation of binary digit. (2) A single character
of a language employing only two distinct kinds of characters.
Blackbody, black body (bb): An ideal emitter which radiates energy
at the maximum possible rate per unit area at each wavelength for any given
temperature. A blackbody also absorbs all the radiant energy incident upon
it. No actual substance behaves as a true blackbody.
Blackbody radiation: The electromagnetic radiation emitted by an
ideal blackbody; it is the theoretical maximum amount of radiant energy
of all wavelengths that can be emitted by a body at a given temperature.
The spectral distribution of blackbody radiation is described by Planck's
law and related radiation laws.
BRDF: Bidirectional Reflectance Distribution Function (see above)
BRF: Bidirectional reflectance factor (see above).
Brightness: The attribute of visual perception by which an area appears
to radiate more or less light.
Brightness temperature: Temperature of a blackbody that gives the
same radiance in a narrow range of wavelengths as the object being studied.
Brightness value: A image pixel value that represents the amount
of radiance striking a detector in a multi-spectral scanner.
BSQ: Band Sequential. Multi-channel image format where the complete image data for each channel is grouped together, and the file contains a sequence of these distinct channels, that is:
for m lines and n channels in the image.
Bug: Colloquial computing term for a mistake in a program.
Byte: Amount of computer memory space needed to store one character,
usually 8 bits. The size of a computer's memory is usually expressed in
Megabytes (Mb), with 1 Mb being 1,048,576 bytes.