ERDAS Imagine is a software package designed for working with GIS raster data. It has its own binary “img” format for images. The content of this file can vary: it can be a georeferenced image or a GIS grid file.
The .img file can be associated with corresponding files: .rrd, .xml.
Various GIS applications can open data from ERDAS IMAGINE. However, the accessibility and interoperability of the data is relatively limited. IMG is directly linked to a commercial package and not an open format.
For the long term, it is advisable to export the data to an open, wider supported format.
It is recommended to save a georeferenced image as GeoTIFF.
It is recommended to convert Grid files to ASCII text.
Note: Grid files from ERDAS can be built in “multiband”. This can mean that separate colors are recorded in separate “bands”. A Grid conversion in applications such as ArcGIS and MapInfo often focuses automatically on the first band. Other bands can be selected separately.
In addition, an IMG Grid file can be provided with coloring that would be lost with direct export to ASCII. This coloring is accessible as tabular data within GIS applications and can be exported and treated separately. It is recommended to save this color information (“attribute table” / “color map”) as a CSV file.
When converting ERDAS IMAGINE Grid files it is extra important to check for completeness by comparing the export with the original.
ERDAS IMAGINE File Format is a non-preferred format for file type raster GIS and a non-preferred format for file type Images (georeference).