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Data structures
Can a property ownership map be related to a satellite image, a timely indicator of land uses? Yes, but since digital data are collected and stored in various ways, the two data sources may not be entirely compatible. So a GIS must be able to convert data from one structure to another.
Image data from a satellite that has been interpreted by a computer to produce a land use map can be "read into" the GIS in raster format. Raster data files consist of rows of uniform cells coded according to data values. An example would be land cover classification.
Raster data files can be manipulated quickly by the computer, but they are often less detailed an may be less visually appealing than vector data files, which can approximate the appearance of more traditional hand-drafted maps. Vector digital data have been captured as points, lines ( a series of point coordinates), or areas (shapes bounded by lines).
An example of data typically held in a vector file would be the property boundaries for a housing subdivision.
Data restructuring can be performed by a GIS to convert data into different formats. For example, a GIS may be used to convert a satellite image map to a vector structure by generating lines around all cells with the same classification, while determining the cell spatial relationships, such as adjacency or inclusion.
Thus a GIS can be used to analyze land use information in conjunction with property ownership information.
The content of this page was copied from USGS Website.
For more information please refer to the site: mapping.usgs.gov
