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| 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 | 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 | ||
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| GIS data is commonly in one of two forms: | GIS data is commonly in one of two forms: | ||
Revision as of 15:24, 24 July 2006
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 formatHowever 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. Geometric shapes, including points, lines, and polygons. These might represent buildings, roads, and counties. This link gives sums up the most commonly used general purpose vector formats. http://data.geocomm.com/helpdesk/formats.html#vector-formats
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.
