An easy way to think of how GIS can be applied is to think in terms of the questions that the user might want answers to. As has been mentioned, one of the first steps when setting up a GIS is to survey the potential users to determine their information needs, and to identify those needs that can best be met by a GIS incorporating various combinations of data retrieval and transformation.
The ultimate use of GIS lies in its capability for modeling: constructing models of the real world from digital data bases, and using these models to simulate the effect of a specific process over time for a given scenario. Modeling is a powerful tool for analysing trends and identifying factors that affect them, or for displaying the possible consequences of planning decisions or projects that affect resource use and management.
At the continental level, for example, terrain maps can be combined with hydrologic maps and climatological data to produce maps of land suitability for various types or intensities of use, or specific crops. Demographic and administrative data can be added to provide projections of future supply-and-demand scenarios by region or country.
At the national and local level, possible GIS applications are almost endless. For example, to decide on the best potential sites for growing a certain cash crop, the agricultural planner might use geographic data bases combining soils, topography and rainfall to determine the size and location of biologically suitable areas, and then overlay this with landownership and transport infrastructure, labour availability and distance to market centres. Further, he or she could then change the characteristics of various attributes over time to determine the probable impacts of changing circumstances, such as the effects of a drought, the rise or fall of domestic or world prices, or the development of additional roads.
Modeling, often involves proximity analysis and interpolation. The figure above illustrates an example of a proximity analysis based on Voronoi Polygons. Here Southern Africa was partitioned into Voronoi Polygons ("tessellation") with a meteorological station at the centre of each polygon (or "tile"). Each tile contains that portion of the plane closest to a given meteo station. This diagram was used for estimating water resources. For further information on FAO's water resources assessment activities, see FAO Water Service.
Applications of GIS to fisheries can take many forms. However, it is convenient to categorize them first of all as applications in capture fisheries and in aquaculture. For capture fisheries, GIS can deal with the spatial aspects of the three main fishery "realms", both individually and collectively - the environment, the fishery resources and the fisheries. GIS, using information from a variety of sources, including passive and active remote sensing, can predict where the fish will be, can be used for management, control and surveillance (e.g. monitor fishing) and can optimize fishing operations such as trade-offs between distance to fishing grounds and markets.
In aquaculture, GIS has been used to forecast development prospects using suite of parameters that vary geographically . Basically, this kind of application reduces to two broad questions: a) what is the suitability of any given area for the culture system (e.g., soil suitability for the construction of fish ponds) and b) what is the suitability of an area for fish growth (e.g. favourable temperature regime). Another GIS application is for the management of expanding aquaculture in the context of other, competing uses of land and water. The pertinent question here is: How much is too much?
Below is a map produced by an FAO inland fisheries GIS project.
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| For further information on the project, download A strategic re-assessment of fish farming potential in Africa (Abstract - MS-Word 6.0) |
Forestry planners can use GIS to monitor the impacts of deforestation, and to plan the timing and type of timber management practices based on information on soil types, species requirements, growth and yield, and even to assess the visual impacts of timber harvesting in sensitive scenic areas.
The wildlife manager can use GIS to determine the size and location of animal populations, to map supply-and-demand relationships to meet consumption needs, or to determine areas having high food and habitat potential for specific species.
In summary, what the GIS provides is a means of converting spatial data into digital form that can then be displayed, manipulated, modified and analysed and reproduced quickly in a new format, available for either visual display or hard copy reproduction. Conventional (paper) maps, in contrast, are time-consuming to prepare manually, and the display and analysis of changed data or the comparison of more than one set of map data (soil and vegetation, for example) requires additional manual labour.
The digital data can also be easily transmitted from one user to another or from one GIS to another merely on disk, tape or by the Internet. As digital maps come into wider use, the cost of digitizing can be shared by many users. In fact, some digitized maps on CD-ROMs cost less than the same maps on paper. As networks and libraries of databases grow, information exchange should reduce the need for redigitizing regional or national maps and other geographic databases than are in common use.
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