Geographic information system
A geographic information system (GIS) is typically defined as a computer software package designed to facilitate the analysis and display of geographically referenced spatial data by providing four general capabilities:
- Data input (encoding)
- Data management (i.e. archival, storage, query and retrieval)
- Statistical analysis (both basic data analysis and methods unique to spatial analysis)
- Output (display and input into other software)
All four of these functions involve interactions between the software system and the user, and most modern GIS packages are designed to allow the user to display the data and results associated with each function inside the program (i.e. most packages include a visual display and a graphical user interface, or GUI). GIS is primarily used to analyze spatial data acquired from cartographic records or remote sensing imagery, although GIS could theoretically be used to analyze any type of multidimensional data. [1]
Geographic information systems are a tool utilized by a wide variety of disciplines including resource management, conservation, asset management, cartography, market analysis, logistics, real estate, defense, emergency management, and transportation.
GIS data
Data within a GIS can be represented in two formats - raster and vector. Raster data organizes information in a grid of equal sized cells, with each cell representing an attribute value and a spatial location. Raster is usually used to represent large, generalized datasets such as digital elevation models(DEM). Vector data offers a more specific representation than raster and can contain numerous attributes per feature. Data is represented as points(well locations, traffic accidents), lines(roads, pipelines), and polygons(political boundaries, lakes) with coordinates attached to vertices along the feature.
GIS and Remote Sensing
Because much of the spatial data used in GIS is based on remotely sensed images, the software systems designed for GIS and those designed for the processing of remotely sensed images are intimately related, and many of the major GIS packages include at least basic image processing capabilities, and image processing applications vice versa.
GIS software packages
As with many other software applications, both proprietary systems and open source systems are available. The majority of the proprietary systems are limited to the Microsoft Windows operating system, while the open source systems tend to work with several different OS types.
ArcGIS
ArcGIS is the primary GIS platform developed by Environmental Systems Research Institute, Inc. (ESRI). It is the most commonly used GIS software.
Notes
- ↑ Jensen, J. R. (1996) Introductory Digital Image Processing: A Remote Sensing Perspective. Prentice Hall Series in Geographic Information Science. Clarke, K. C. (ed.). Prentice Hall, Upper Saddle River, New Jersey, United States. 316 p.