A simple data structure-A matrix of pixels with values having a coordinate location that can be linked to an attribute table.However, many other features (such as points) and measurements (such as rainfall) can be stored as either a raster or a feature (vector) data type.Īdvantages of storing data as a raster include the following: ![]() Sometimes you don't have the choice of storing data as a raster for example, imagery is only available as a raster. The image below is an example of a classified raster dataset showing land use. For example, you can process data using a geoprocessing model to create a raster dataset that maps suitability for a specific activity. ![]() Thematic maps can also result from geoprocessing operations that combine data from various sources, such as vector, raster, and terrain data. This groups the values of multispectral data into classes (such as vegetation type) and assigns a categorical value. A common analysis application is classifying a satellite image into land-cover categories. Rasters representing thematic data can be derived from analyzing other data. The raster in the image below displays elevation-using green to show lower elevation and red, pink, and white cells to show higher elevation. Elevation values measured from the earth's surface are a common application of surface maps, but other values, such as rainfall, temperature, salinity, magnetic properties, and density of materials can also define surfaces that can be spatially analyzed. They also provide a regularly spaced representation of surfaces. They provide a method of storing the continuity as a surface. Rasters are well suited for representing data that changes continuously across a landscape (surface). The following image is used as a basemap for road data. The main sources of raster basemaps are orthorectified images from aerial, drone, and satellite imagery, and scanned maps. For example, orthoimages that are displayed under other GIS layers allow map users to confirm that map layers are spatially aligned and represent real objects, as well as provide additional contextual information. In a GIS, image and raster data is typically used for the following:Ī common use of image data in a GIS is as an image background for other feature layers. Image and raster data is useful for a wide range of applications. They can be displayed with geographic data and are used to convey additional information about map features. Thematic and digital pictures are often used as attributes in tables.
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