Map algebra
Encyclopedia
Map algebra is a simple and an elegant set based algebra
for manipulating geographic data, proposed by Dr. Dana Tomlin
in the early 1980s.
It is a set of primitive operations in a Geographic Information System
(GIS) which allows two or more raster
layer
s ("maps") of similar dimensions to produce a new raster layer (map) using algebraic operations such as addition, subtraction etc.
Depending on the spatial neighborhood, GIS transformations are categorized into four classes: local, focal, global, and zonal. Local operations works on individual raster cells, or pixel
s. Focal operations work on cells and their neighbors, whereas global operations work on the entire layer. Finally, zonal operations work on areas of cells that share the same value. The input and output for each operator being map, the operators can be combined into a procedure, script, to perform complex tasks.
Algebra
Algebra is the branch of mathematics concerning the study of the rules of operations and relations, and the constructions and concepts arising from them, including terms, polynomials, equations and algebraic structures...
for manipulating geographic data, proposed by Dr. Dana Tomlin
Dana Tomlin
Dana Tomlin is an author, professor, and originator of map algebra. Tomlin's teaching and research focus on the development and application of geographic information systems . He is Founder and Co-Director of Penn’s , and author of . The Map Algebra language he created is embodied in most of...
in the early 1980s.
It is a set of primitive operations in a Geographic Information System
Geographic Information System
A geographic information system, geographical information science, or geospatial information studies is a system designed to capture, store, manipulate, analyze, manage, and present all types of geographically referenced data...
(GIS) which allows two or more raster
Raster graphics
In computer graphics, a raster graphics image, or bitmap, is a data structure representing a generally rectangular grid of pixels, or points of color, viewable via a monitor, paper, or other display medium...
layer
Layers (digital image editing)
Layers are used in digital image editing to separate different elements of an image. A layer can be compared to a transparency on which imaging effects or images are applied and placed over or under an image...
s ("maps") of similar dimensions to produce a new raster layer (map) using algebraic operations such as addition, subtraction etc.
Depending on the spatial neighborhood, GIS transformations are categorized into four classes: local, focal, global, and zonal. Local operations works on individual raster cells, or pixel
Pixel
In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
s. Focal operations work on cells and their neighbors, whereas global operations work on the entire layer. Finally, zonal operations work on areas of cells that share the same value. The input and output for each operator being map, the operators can be combined into a procedure, script, to perform complex tasks.