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Introduction to GIS and formats

GIS

In order to work effectively with large quantities of data the use of geographic information systems (GIS) is necessary.

Geographic Information Systems (GIS) are a computer programs that organize, display, and analyze spatially distributed data. At its simplest, GIS is "mapping", providing a geographic arrangement of extremely diverse information. GIS has been applied in geology, biology, psychology, anthropology etc., and has been around in Crop Forecasting for a long time.

General purpose GIS programs are designed to capture and analyze any kind of geographical data. The most common commercial GIS software packages worldwide are:

Raster  format
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Raster format

However the open-source community has created a wide range of free tools (to be downloaded from the internet). A nice start page can be found here: http://www.mapcruzin.com/free_gis.htm

Data

GIS data is commonly in one of two forms:

  • Raster or image format. A grid of rows and columns of cells. These might represent photographic or scanned images. Within agrometeorology satellite images are usually represented in this way. Each cell represents a value. This value can be assigned a thematic colour in order to visualize the data. Raster data come in a large number of file types. A good overview of raster file types can be found here: http://data.geocomm.com/helpdesk/formats.html#raster-formats
Vector format
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Vector format



Either of these can have tables of data associated with them, e.g. elevation, population, financial values, etc. Such associated data can be used to color a map so that it conveys information with visual impact.




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