m: Abbreviation for metre(s).
M: (1) Abbreviation for Mega (106). (2) Abbreviation for Megabyte(s).
Magnetic disk: An information storage medium upon which information
is recorded on the magnetic surface of a rotating disk, with associated
reading and writing heads that are mounted on movable arms.
Magnetic tape: A long strip of mylar, plastic-coated with ferrous
oxide, upon which information may be stored or read.
Map: A representation in a plane surface, at an established scale,
of the physical features (natural, artificial, or both) of a part of the
Earth's surface, with the means of orientation indicated.
Map grid: Two sets of parallel lines at right angles drawn on a plane
surface and used as a rectangular co-ordinate system for plotting position
and scaling distances and directions in surveying and mapping; may or may
not be based on map projection.
Map, thematic: A map designed to demonstrate particular features
or concepts. In conventional use this term excludes topographic maps.
Map topographic: A map showing correct horizontal and vertical positions
of features represented.
Marine Observation Satellite (MOS): An unmanned, Japanese polar-orbiting
satellite, carrying sensors specifically designed for oceanographic applications.
Mask: (1) A sheet of thin black paper, metal, or celluloid normally
used to obtain white margins on a photograph. (2) Any material used over
a print or negative to obscure a part of the image. (3) A raster representation
of a region.
Masking: Process of removing part of an image using a region mask.
Matrix: A rectangular table containing X rows and Y columns used
to display an array of X by Y numbers.
Maximum Likelihood Classifier: Characterises each class by a probability
distribution function and allocates pixels to the class with maximum likelihood
among the candidate distributions. The most common model for the probability
distribution function is the Gaussian distribution in which each class is
characterised by its mean and covariance matrix.
Mb/Mbytes: Abbreviation for Megabyte(s).
Mean image: A classified image in which the values of each pixel
are represented by the mean values of the spectral class to which it was
allocated.
Median filter: A spatial filter implemented by convolution which
substitutes the median value from surrounding pixels for that recorded at
an individual pixel. It is useful for removing random noise.
Megabyte: 2^20 or 1,048,057 bytes. Commonly used to express computer
disk or tape capacity.
MESSR: Multi-spectral, Electronic, Self-Scanning Radiometer; carried
on Japanese MOS-1 satellite.
Metamer: Colour which is perceived to be the same as another colour
even though they have different spectral energy distributions. Metamers
may look the same under one lighting condition, and show their difference
under another condition.
Meteosat: European geostationary meteorological satellite.
micro (µ): Standard prefix indicating 10^-6.
microBRIAN: An applications-based image processing system developed
by CSIRO Australia and MPA International Pty Ltd.
Micron: Equivalent to and replaced by micrometer; 10^-6 m.
Middle infrared: See infrared.
Mie scattering: Multiple reflection of radiation by atmospheric particles
that have the approximate dimensions of the radiation wavelength.
Mie theory: A complete mathematical-physical theory of the scattering
of electromagnetic radiation by spherical particles, developed by G. Mie
in 1908. In contrast to Rayleigh scattering, the Mie theory embraces all
possible ratios of diameter to wavelength. The Mie theory is very important
in meteorological optics, where diameter-to-wavelength ratios of the order
of unity and larger are characteristic of many problems regarding haze and
cloud scattering. Scattering of radar energy by raindrops constitutes another
significant application of the Mie theory.
milli (m): Standard prefix indicating 10^-3.
Minimum distance classifier: A classification technique that assigns
raw data to the class whose mean falls the shortest Euclidean distance from
it.
Minus-blue photograph: A panchromatic black-and-white photograph
from which the blue part of the visible range has been removed using a yellow,
or minus- blue, filter.
MIR: Middle infrared.
Mixed pixel: A pixel whose value represents the average energy reflected
or emitted by several types of surface present within the area that it covers
on the ground.
Mixel: When an image pixel falls into more than one land cover type
on the ground, the radiance values for that pixel are a mixture of the different
land cover radiance values and the pixel is therefore called a mixel.
mm: Abbreviation for millimetre. 1 mm equals 1 x 10^-3 m.
MODIS: MODerate resolution Imaging Spectrometer.
Modular Optical-Electronic Multi-spectral Scanner (MOMS): An imaging
system from the Federal Republic of Germany, carried experimentally on Space
Shuttle missions and which is based on pushbroom systems.
MOMS: Modular Optical-Electronic Multi-spectral Scanner; carried
on Space Shuttle.
Monochromatic: Pertaining to a single wavelength or, more commonly,
to a narrow band of wavelengths.
MOS: Marine Observation Satellite.
Mosaicking: The assembling of photographs or other images whose edges
are cut and matched to form a continuous photographic representation of
a portion of the Earth's surface.
MSS: Multi-Spectral Scanner.
MSU: Microwave Sounding Unit; part of the TOVS package on the NOAA
satellites.
Multi-band system: A system for simultaneously observing the same
(small) target with several filtered bands, through which data can be recorded.
Usually applied to cameras; may be used for scanning radiometers that use
dispersant optics to split wavelength bands apart for viewing by several
filtered detectors.
Multi-channel system: Usually used for scanning systems capable of
observing and recording several channels of data simultaneously, preferably
through the same aperture.
Multi-spectral: Generally used for remote sensing in two or more
spectral bands, such as visible and IR.
Multi-spectral (line) scanner: A remote sensing device that operates
on the same principal as the infrared scanner, except that it is capable
of recording data in the ultraviolet and visible portions of the spectrum
as well as the infrared.
Multi-temporal: Of, or pertaining to, one or more than one time or
period, as multi-temporal analysis or observations; indicating studies,
usually of the same area or object, carried out at specific time intervals.
Multi-temporal images: Images which contain the same wavelength channels
of the same ground area but which were taken at different times.
Multi-variate analysis: A data analysis approach that makes use of
multi- dimensional interrelations and correlations within the data for effective
discrimination.
Munsell system: A perceptual colour system which identifies colour
in terms of hue, value and chroma, arranged in orderly scales of equal visual
steps. A notation assigning a numerical equivalent to each attribute on
its scale yields a unique designation for any given colour. Standardised
colour chips sampling the Munsell colour space and labelled by Munsell notation
are used internationally to express the perceived colour of an object, to
match colours, etc.