What is a raster type?

Raster data is added to a mosaic dataset by specifying a raster type. The raster type identifies metadata, such as georeferencing, acquisition date, sensor type, and band wavelengths, along with a raster format. A raster format defines how pixels are stored, such as number of rows and columns, number of bands, actual pixel values, and other raster format-specific parameters. However, by adding raster data according to a raster type, the appropriate metadata is read and used to define any processing that needs to be applied. For example, when adding a QuickBird Standard scene, a scene may be defined by a .imd file. The .imd file contains metadata information about the raster dataset and may point to one or more .tif files. To add this data correctly, use the QuickBird raster type because it searches for this combination of file types. If you add the raster data using the Raster Dataset raster type, only the .tif files will be recognized and added; they will be added as TIFF files, and any metadata information that can affect the needed functions or the georeferencing will be missing.

The Raster Dataset raster type refers to any raster format supported by ArcGIS. The other raster types are specific to a product (sensor, data provider, or vendor) or the associated metadata information. You have the option to edit any raster type when adding data. For example, you might want to define a specific band combination, pan-sharpening algorithm, or add a filter when the data is added, rather than later. You can modify any raster type by changing its default properties, such as the band combination, or defining the elevation model to use when orthorectifying data. You can even add or modify the function chains. Anytime you make an edit to the raster type when adding rasters to a mosaic dataset, you can save it to a new .art file so you can load additional data at another time using the same modified parameters. Optionally, you can save it as a .art.xml if you want to read or modify it directly.

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