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WEEK 9
TOPIC: GIS DATA.
CONTENT
- Sources of data
SOURCES OF DATA
GIS data are the geographic information used for geographical analysis. There are various sources of data in GIS. They are: land survey, remote sensing, map digitizing, map scanning, field investigation, tabular data, etc.
- Land Survey: This is a source of geographic data that is derived from the use of survey instrument using a technique called coordinate geometry. For example, Global Positioning System (GPS) is one of the survey instruments used in capturing data.
- Remote Sensing: This is the perception and recording of phenomena by devices which are not in contact with them. That is, it means obtaining information about land, water, or an object without physical contact between the sensor and the object of analysis. Also, it is the collection of data by instruments carried abroad aircraft or satellite. Remote sensing system is commonly used to survey, map and monitor the resources and environment of earth. Several different types of remote sensing device are used which include; camera, multispectral scanner, etc.
- Map Digitising: This has to do with the use of topographical map as a source of data. To digitalise a map, it has to be checked within theoretical dimension, then scanned into a raster format and resulting raster data has to be given a theoretical dimension by a rubber sheeting/warping technological process.
- Map Scanning: The map scanning is the process of converting paper maps into digital format usable by computer.
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