An .ovr file is used for storing the pyramid layers for a raster dataset (it is a replacement of the .rrd). An .ovr file is created if the following conditions exist:
- The file format is not an ERDAS IMAGINE (.img) file.
- The pyramids are built with ArcGIS 10 or later.
One benefit of the .ovr file over the .rrd file is you can control the compression type and quality of the pyramids.
OVR file requirements
A requirement for building an .ovr file for a raster dataset is to have write access to the directory where the dataset resides. The .ovr file will be created in the same directory as the source dataset when you choose to build pyramids. The next time you add this raster dataset, these pyramids will be used.
OVR file size
For uncompressed rasters, the .ovr file size is approximately 8 percent of the size of the original raster dataset. The size of the .ovr file created can be compressed, so the overview file size will be dependent on the compression technique used.