A raster-based GIS uses a grid to represent image data and can collect, store, and analyze data for various fields. It is useful for representing data that can be measured at any point and can create new layers using algebraic equations. Remote sensing technology has improved the ease of collecting raster GIS data, but linear features are difficult to represent accurately.
A geographic information system (GIS) is a computer system that handles various forms of data that deal with advanced cartography. It can, among other things, collect, store and analyze data for use in a variety of fields, such as urban planning and archeology. A raster-based GIS, or simply raster GIS, uses a combination of map data and imagery to provide a complete representation of the studied area. A grid is used to represent the image data, and calculations can be performed with the data to reveal relationships between target area attributes. Raster GIS is commonly used to classify vegetation, land use and urban change over a particular area.
Raster GIS has the advantage of being able to collect data for all geographic features, images and surfaces. Such systems are useful for representing data that can be measured at any point, such as temperature and elevation. A raster cell records information about the interior of the cell and boundaries are created by adjacent cells.
A raster-based GIS represents datasets by dividing a map into equally sized cells aligned in a grid. Cells can be assigned a value used to represent some location characteristic, and all cells in a dataset make up a layer or raster. The layered and cell format of the raster GIS dataset allows you to place multiple data in the same location. When layers are stacked, relationships are formed between different datasets that occupy the same cell. The ability to compare the relationships within different cells of a given area is what makes raster GIS such a useful tool.
A GIS engineer can use overlaid raster GIS layers to create new layers using algebraic equations. Algebraic equations, or map algebra, allow you to create new layers using information from the GIS system to eliminate areas of land that do not meet user-defined criteria. The ability to stack layers of information makes raster GIS a great tool for determining sites that meet specific requirements.
Advances in aeronautical and satellite technology have enabled vast improvements in the ability and ease of using remote sensing to collect raster GIS data. Remote sensing instruments are attached to aircraft and satellites and, from there, collect different types of image data. Remote sensing instruments can detect and record both visible data and any measurable part of the electromagnetic spectrum.
The downside of this system is that linear features, such as rivers, are difficult to represent accurately. The size of the cell determines how accurately boundaries and features are represented. A smaller cell allows for more precise boundaries but requires more data processing.
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