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Introduction to GIS

GIS is a System of computer software, hardware and data, and personnel to help manipulate, analyze and present information that is tied to a spatial location 

• spatial location usually a geographic location information
• visualization of analysis of data system
• linking software, hardware, data 

 

Data Structures

Two main types of data structures: Raster and Vector

 

Vector data consist of points, lines (arcs) and polygons formed from lines joining x and y coordinates. Most map data are supplied as vectors.

Point: Each point represents a feature on the map and is created by (x, y) coordinates, and is stored as an individual record in the shapefile

Line: Formed by connecting two data points. (The system stores one end of the line as the starting point and the other as the end point, giving the line "direction". )

Polygon: An area fully encompassed by a series of connected lines. (Multi-sided Shape)

Raster data are organised in grids, one value per grid square. All photographs and images are raster. Map data can be converted to raster usually for purposes of analysis, which is faster and easier in raster than vector.

 

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