File-based Raster/Image Format

File-based raster/image format is common in GIS platforms. Common extensions are: TIF, IMG (ERDAS Imagine), and JPG – a compressed format). All of these require a georeference for use in a GIS platformk that provides the spatial reference for use with other spatial map layer formats. BMP, GIF, and PNG are typically NOT used in GIS platforms other than for icon symbols.

The screenshot below shows an example of a TIF file. The RRD (or OVR) and AUX files are additional files that often get created when loading a TIF file into a GIS platform for the first time. The RRD (or OVR) file is referred to a “pyramid layer” (created by ERDAS Imagine, the OVR file is created by ArcGIS) and allows for additional scales of the image to be loaded when the map scale changes when one zooms in/out of a map viewer. The AUX file is an “auxiliary” file that can contain other information related to the spatial reference, image statistics, and color ramps.

Raster File Formats

Pyramid Layers

Auxiliary Files

Raster Dataset

Raster Dataset is a format used in file and enterprise geodatabase. Note – no “file extension” is shown.  Raster dataset is a raster format type, not a file-based raster format such as TIF or IMG. The screenshot below shows an example of a raster data set stored in a file geodatabase.