Encyclopedia of Computer Science and Technology

208 Geographical Information SystemsApplicationsVariations of genetic algorithms or “evolutionary programming”have been used for many applications. In engineeringdevelopment, a virtual environment can be set up in whicha simulated device such as a robot arm can be allowed toevolve until it is able to perform to acceptable specifications.(NASA has also used genetic programs competing on80 computers to design a space antenna.) Different versionsof an expert system program can be allowed to compete atperforming tasks such as predicting the behavior of financialmarkets. Finally, a genetic program is a natural way tosimulate actual biological evolution and behavior in fieldssuch as epidemiology (see also artificial life).Further Reading“Bibliography on Genetic Programming.” Available online. URL: http://liinwww.ira.uka.de/bibliography/Ai/genetic.programming.html. Accessed August 5, 2007.Brown, Chappell. “Darwin’s Ideas Evolve Design.” EE Times, February6, 2006. Available online. URL: http://www.eetimes.com/showArticle.jhtml?articleID=178601156. Accessed August 5,2007.Eiben, A. E., and J. E. Smith. Introduction to Evolutionary Computing.New York: Springer, 2003.Genetic-programming.org [Resources]. Available online. URL: http://www.genetic-programming.org/. Accessed August 5, 2007.“The GP Tutorial.” Available online. URL: http://www.geneticprogramming.com/Tutorial/. Accessed August 5, 2007.Keats, Jonathon. “John Koza Has Built an Invention Machine.”Popular Science, April 2006. Available online. URL: http://www.popsci.com/popsci/science/0e13af26862ba010vgnvcm1000004eecbccdrcrd.html. Accessed August 5, 2007.Langdon, William B., and Riccardo Poli. Foundations of GeneticProgramming. New York: Springer, 2002.Riolo, Rick, and Bill Worzel, eds. Genetic Programming Theoryand Practice. Norwell, Mass.: Kluwer Academic Publishers,2003.Geographical Information SystemsCartography, or the art of mapmaking, has been transformedin many ways by the use of computers. Traditionally,mapmaking was a tedious process of recording, compiling,and projecting or plotting information about the location,contours, elevation, or other characteristics of natural geographicfeatures or the demographic or political structureof human communities.Instead of being transcribed from the readings of surveyinginstruments, geographic information can be acquiredand digitized by sensors such as cameras aboard orbitingsatellites. The availability of such extensive, detailedinformation would overwhelm any manual system of transcribingor plotting. Instead, the Geographical InformationSystem (GIS, first developed in Canada in the 1960s)integrates sensor input with scanning and plotting devices,together with a database management system to compilethe geographic information.The format in which the information is stored is dependenton the scope and purpose of the information system. Adetailed topographical view, for example, would have physicalcoordinates of latitude, longitude, and elevation. On theother hand, a demographic map of an urban area mightA raster grid showing annual rainfall totals in inches for mythicalSquare County. Raster data is easy to work with, but the “coarseness”of the grid means that it does not capture much local variationor detail.have regions delineated by ZIP code or voting precinct, orby individual address.Geographic data can be stored as either a raster or avector representation. A raster system divides the area intoa grid and assigns values to each cell in the grid. For example,each cell might be coded according to its highest pointof elevation, the amount of vegetation (ground cover) it has,its population density, or any other factor of interest. Thesimple grid system makes raster data easy to manipulate,but the data tends to be “coarse” since there is no informationabout variations within a cell.Unlike the arbitrary cells of the raster grid, a vector representationis based upon the physical coordinates of actualpoints or boundaries around regions. Vector representationis used when the actual shapes of an entity are important,as with property lines. Vector data is harder to manipulatethan raster data because geometric calculations must bemade in order to yield information such as the distancebetween two points.The power of geographic information systems comes fromthe ability to integrate data from a variety of sources, whetheraerial photography, census records, or even scanned papermaps. Once in digital form, the data can be represented in avariety of ways for various purposes. A sophisticated gis canbe queried to determine, for example, how much of a proposeddevelopment would have a downhill gradient and bebelow sea level such that flooding might be a problem. Theseresults can in turn be used by simulation programs to determine,for example, whether release of a chemical into thegroundwater from a proposed plant site might affect a particulartown two miles away. Geographic information systemsare thus vital for the management of a variety of complexsystems that are distributed over a geographical area, suchas water and sewage systems, power transmission grids, andtraffic control systems. Other applications include emergencyplanning (and evacuation routes) and the long-term study ofthe effects of global warming trends.