Gis

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Components of GIS

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*Hardware (computers)

*software (computer programmes) *data (information)

*people

*procedures (how to solve a problem or answer a question)

*network (where to get the information from).

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Spatial data

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Spatial data refers to the position of an object, in other words, its co-ordinates.For example, the spatial data for a tree could be: 29°30,3' S; 19°10,8' E

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Attribute data

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Attribute data is information that describes or gives the characteristics of an object.For example, the attribute data for a tree could be: It is an acacia tree, which is 5 m tall.

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Vector data

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Spatial data stored in the form of co-ordinates, shown as point, line or polygon features.

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Point features

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Point features on a map include spot height, buildings and trig. stations.

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Line features

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Line features on a map include rivers, roads and walls.

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Polygon features

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Polygon features on a map include cultivated land, built-up areas and dams.

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Buffering

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To demarcate (mark off) an area around an object.

The marked-off area is the buffer zone. Buffer zones often protect people from living in a dangerous area.For example, along a river people should live above the 50-year fl ood line. The 50-year fl ood line is the height below which the river fl oods. The area below the 50-year fl ood line is the buffer zone for this area. If you live in the buffer zone your home is likely to be affected when the river fl oods. If you take notice of the buffer zone and live above the 50-year fl ood line, your home is likely to be safe when the river fl oods.

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Raster data

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Spatial data stored in the form of pixels. Pixels are similar to the blocks found on a topographic map (e.g. block A3). The size of the pixel (block) will determine in how much detail an area will be shown. Smaller pixels show more detail. Larger pixels show less detail.

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Remote sensing

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Taking a picture of something from far away, for example from a satellite.

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Spatial resolution

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How clear and easy the detail is to see.

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Data or thematic layering

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When different kinds of information are placed one on top of the other to see the overall picture.For example, on the Nelspruit map, the layers of data needed to draw block D1 are:• Vegetation • Contour lines • Roads • Power lines • Built-up areas • Water Figure 5.5.2 illustrates the idea of data layering.

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Data standardisation

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It is the process of achieving agreement on common data definitions, representation and structures to which all data layers must conform.

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Data querying

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This is a process used to retrieve or get data from the data base.

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Statistical analysis

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The collection of methods used to process large amounts of data and report overall trends.Customers Buildings Streets Reality