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To georeference means to associate something with locations in physical space. The term is commonly used in the geographic information systems field to describe the process of associating a physical map or raster image of a map with spatial locations. Georeferencing may be applied to any kind of object or structure that can be related to a geographical location, such as points of interest, roads, places, bridges, or buildings. Geographic locations are most commonly represented using a coordinate reference system, which in turn can be related to a geodetic reference system such as WGS-84. Examples include establishing the correct position of an aerial photograph within a map or finding the geographical coordinates of a place name or street address (Geocoding). ==Need== *Georeferencing is crucial to making aerial and satellite imagery, usually raster images, useful for mapping as it explains how other data, such as the above GPS points, relate to the imagery. *Very essential information may be contained in data or images that were produced at a different point of time. It may be desired either to combine or compare this data with that currently available. The latter can be used to analyze the changes in the features under study over a period of time. *Different maps may use different projection systems. Georeferencing tools contain methods to combine and overlay these maps with minimum distortion. *Using georeferencing methods, data obtained from surveying tools like total stations may be given a point of reference from topographic maps already available. *It may be required to establish the relationship between social survey results which have been coded with postal codes or street addresses and other geographic areas such as census zones or other areas used in public administration or service planning. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Georeference」の詳細全文を読む スポンサード リンク
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