An AUX file holds metadata for non-ERDAS IMAGINE raster file formats (IMG). Much of the metadata is extensive and cannot be stored in files such JPEG, TIFF, etc. ESRI licenses AUX from Leica Geosystems. If the user deletes it, while it will be recreated with display and processing, much of the metadata will be lost. IMG is a raster data file created within ERDAS IMAGINE, a Geospatial Imaging program. The IMG data file holds all image and metadata in one container. Some data contained with a typical IMG file are: image data, image statistics, database attributes, transformations, ground control points, reduced resolution layers (aka pyramid layers), map coordinates, horizontal and vertical projection and datum, processing genealogy, and LUT stretches. These same data may be conatined in AUX files if the user wishes to use data formats other than IMG.