M
Macro
A text file containing a sequence of commands that can be executed as one command. Macros can be build to perform frequently used, as well as complex operations. The ARC Macro Language (AML) is used to creat Mocros for ARC/INFO
Map
An abstract representation of the physical features of a portion of the Earth's surface graphically displayed on a planar surface. Maps display signs, symbols and spatial relationship among the features. They typically emphasize, generalize and omit certain features from the display to meet design objectives. (eg railroad features might be included in transportation map but omitted from a highway map.)
Map Generalisation
The process of reducing details on a map as a consequence of reducing the map scale. The process can be semi - automated for certain kinds of data, such as topographical features, but requires more insight of the thematic maps.
mapping unit
See - soil mapping unit
map projection
"A device for representing all or part of a rounded surface on a flat sheet. Since this cannot be done without distortion, the cartographer must choose the map characteristic (area, shape, scale, direction) which is to be shown accurately at the expense of others." Map Projections Used by the U. S. Geological Survey, Geological Survey Bulletin 1532, Second Edition, U. S. Government Printing Office, Washington, D.C., 1982, p. 5. The map projection geometrically or mathematically generates the grid of lines of latitude and longitude.
Every process that establishes or translates map projections offers the same standard selection list of projections. The practical choice of map projections for ungeoreferenced project materials is normally determined by the kind of projection used by those project materials that are calibrated to a projection. For example, if you have a scanned USGS topo map in the polyconic projection, you may decide to calibrate (or translate existing calibration) satellite images and vector overlays to the same projection. (See also: ellipsoid.)
map quadrangle or map quad
The geographic area covered by a map. One kind of map quadrangle is the 7.5' x 7.5' area that is covered by a standard USGS 7.5' topographic map. Referring to a 7.5' map quadrangle does not imply the presence of an actual paper map. The term may simply designate the area covered by electronically stored materials.
Map query
The process of selecting information from a GIS by asking spatial or logical questions of the geographic data. Spatial query is the process of selecting features based on location or spatial relationship (eg select all features with 300 feet of another, point a set of feature to select there). Logical query is the process of selecting features whose attributes meet specific logical criteria (eg, select all polygons whose value for area is greater than 10,000 or select all streets whose name is main st.') Once selected additional operation can be performed, such as clearing them, listing their attributes or summarizing attribute values.
map scale
The relationship that exists between a distance on a map and the corresponding distance on the earth. It may be expressed as an equivalence, one inch equals 16 statute miles; as a fraction or ratio, 1:1,000,000; or as a bar graph subdivided to show the distance that each of its parts represents on the earth.
marking features
Saving prototype areas that have been classified in feature mapping, clustering, or some other interpretation process as permanent features. Marked features can be unmarked. (See also: labeling)
mask or data mask
A processing barrier or boundary that only allows selected data values (perhaps in a chosen range or area) to pass. Users might choose a data mask that blocks all values outside a selected value range, eliminating all image features except those in the range they want to use in a process. A mask is more often used to confine the effects of a process to a selected area of a raster object. (See also: processing mask.)
maximum-likelihood classification
A supervised image processing routine usually applied to multivariable images that have a dimensionality greater than 3. First, the user selects sample areas, (called prototype or training set areas) for each feature to be mapped. The maximum-likelihood process then computes the statistical properties of these features. Similarly, it determines the statistical characteristics which separate feature types. After this identification model has been built, the process tests each cell to determine in which prototype group it most probably belongs. A threshold can be set so that if the highest probability of a feature match is below the threshold, the cell is designated as unknown. This "catch-all" group insures that a cell representing a feature type not defined in one of the training sets will not be forced into membership.
MCA
Micro Channel Architecture. The bus architecture used for IBM PS/2 Micro Channel machines.
megabyte, Mbyte, or MB
A unit of measurement for (approximately) 1,000,000 bytes, 1,000 kilobytes, .001 gigabytes, or .000001 terabytes. (See also: bit, byte, exabyte, gigabyte, kilobyte, pecabyte, terabyte.)
menu
A pulldown or popup list of selection options.
menu bar
A graphic component at the top of a window that displays the titles of the pulldown menus.
meridian
A great circle on the earth's surface that passes through the terrestrial poles.
message box
A type of dialog box that contains a message or warning provoked by a user request or processing condition. The user must respond (for example by selecting the OK push button) before the interrupted process can resume.
MI
MicroImages, Inc.
MICROPIPS
A raster-based microcomputer image processing system developed and distributed by the Telesys Group, Inc. This inexpensive entry-level system runs on standard color display cards such as the CGA and EGA and uses a menu-driven interface. MICROPIPS is a well-documented choice for users who want a good training vehicle.
MIDI
Musical Instrument Digital Interface.
minimum distribution angle
An unsupervised classification or clustering process developed by Dr. Jack Paris and presented in: Jack F. Paris and Helenann H. Kwong (1988) Photogrammetric Engineering and Remote Sensing 54(8):1187-1193. Characterization of Vegetation with Combined Thematic Mapper (TM) and Shuttle Imaging Radar (SIR-B) Image Data.
min/max box
A rectangle that encloses a vector or CAD element such that the edges of the box indicate a minimum or maximum coordinate value for that element.
minute or '
"The sixtieth part of a degree of angular measurement, often represented by the sign ' as in 12° 30', read 12 degrees, 30 minutes" (Random House). USGS quadrangle maps are common in both 15 and 7.5 minute sizes. For example, the 7.5 minute map for Crow Butte, Nebraska covers from 103° 15' to 103° 22' 30" west, and 42° 37' 30" to 42° 45' north. (See also: arcsecond, degree.)
mnemonic
A single keyboard character associated with a labeled component (such as a push button or menu selection). The mnemonic is underlined in the label, or if the mnemonic is not contained in the label, it can follow the label in parentheses. The underscore in the menu selection "View", for example, indicates that the letter "V" is the mnemonic for that selection, and that pressing the "V" key on the keyboard will activate the View selection. (See also: accelerator.)
model area
The area of overlap in a pair of stereo images that is selected for creation of a DEM.
monochrome image
An image displayed in a single color or shades of a single color. Most monochrome computer displays use white, green, or amber, although it could be any one color.
montage
A process in the Mosaic process that assembles individual images into a single raster object without regard for geographic or other inherent spatial relationships. Tiling is a similar process, but assumes that the objects to be assembled have parallel grids and equal scales, and so may be accurately joined. (See also: mosaic, tiling)
mosaic
A large image assembled from segments. Each segment may come from a different source and have a different cell size and angle of orientation, but all the segments must be geometrically rectified and calibrated to a common coordinate framework. The mosaic process rotates and re-scales each piece and creates a single combined object. If all segments are georeferenced to the same map projection, they can be automatically mosaicked based upon their geographic calibration without additional adjustments. Recognized verbal forms of mosaic are mosaic, mosaicked and mosaicking. Montaging and tiling do not re-scale or rotate image segments. (See also: montage, tiling.)
MOSS
Map Overlay and Statistical System. A pioneer vector-based geographic information system (GIS) developed and still widely used by groups in the USDI, especially the USF&WS and BLM. MOSS vector data files contain strings of coordinate pairs which describe closed polygonal areas, lines, and single point features. Common boundaries between adjacent polygons are repeated twice in this data structure, once with each polygon. Much geographic data is available in this format, especially that portion of the NWI wetland maps which have been digitized.
motherboard
The main circuit board in a microcomputer. The motherboard normally contains the main processor, logic chips, memory, and expansion slots for optional circuit cards.
mouse
A computer graphics pointing device. As you move a mouse across the desktop, the mouse cursor moves across the image display.
mouse cursor
Shows the position of mouse activity or focus on the screen. The mouse cursor changes shapes to show the function currently assigned to the mouse. For example, an arrow pointer indicates that the mouse may be used for selection. An hourglass or clock shape shows that the mouse is inactive during a processing activity.
mouse pointer
See - mouse cursor
MRI
Magnetic Resonance Imaging. A technique used in medicine to collect computer images of internal organs and systems for examination and evaluation. A device used in medicine.
ms (millisecond)
One thousandth of a second. A measure of average disk access time (the time it takes the drive to position the read/write head over the requested track).
MSS
Multi-Spectral Scanner. A sensing device on the Landsat satellite that collects simultaneous images over multiple ranges of the spectrum.
multi-byte strings
Text in some character encoding schemes exceeds the 256-character limitation of single byte encoding. In multi-byte systems, characters are allotted 2 or 4 bytes each.
multilingual application
A computer program that allows the user to mix multiple languages and character sets is said to be multilingual such as a word processor that allows side-by-side columns of English and Japanese, or even mixture of Latin characters within a longer Japanese text. Multilingualization is more complex than internationalization, which limits the program to one local language at a time.
multiple raster set
A set of coextensive raster objects displayed in unison. When the multiple raster display mode is RGB, HIS, or HBS, three objects are included in the set. When the multiple raster display mode is RGBI or RGBB, four objects are included. One object in the set is assigned to each display component.
multisensor images
Coregistered images with the same cell size collected by different sensing devices. For example, a 10-meter SPOT panchromatic image can be coregistered with a resampled Landsat TM image so that their cells correctly match. This combination is called a multisensor image.
multispectral images
Images optically acquired in more than one spectral or wavelength interval. Each individual image is usually of the same physical area and scale but of a different spectral band. The MSS and TM sensors aboard the Landsat satellite both collect simultaneous multispectral images. The TM sensor scans and stores seven individual images in spectral bands ranging from the blue wavelengths up to those in the thermal infrared.
multitemporal images
Coregistered images collected at different times by the same device. For example, airvideo images collected one year apart, digitized, and warped to the same geometry are called multitemporal images and can be analyzed to map the changes between the dates.
multivariable images
An image stored on more than one independent, coregistered raster. For example, a video framegrabbed image stored as independent red, green, and blue rasters is a multivariable image. So too is any multitemporal, multispectral, or multisensor image.