Meta Raster Format
Meta Raster Format is an image and data storage format designed for fast access to imagery within a georeferenced tile pyramid at discrete resolutions. It was originally developed at NASA's Jet Propulsion Laboratory.
It is a composite format, with an image consisting of 3 components:
- MRF metadata file in XML format (file extension: .mrf)
- MRF data file. This is either a "Pile of PNGs" (file extension: .ppg) or a "Pile of JPEGS" (file extension: .pjg). The data file contains blocks of concatenated images in PNG or JPEG format.
- MRF index file (file extension: .idx)
In addition, recent versions of the format are reported to support Limited Error Raster Compression (LERC), which was developed at ESRI. However, the current (checked January 2016) version of the filespec does not mention LERC yet.