About EVI files
EVI files are created by Echoview in order to speed up access to echosounder data files. They contain a summary, or index, of the data in the original file. Once created, Echoview will refer to the index file for many operations rather than reading the original data file.
Depending on the type of data file, and specific data stored within it, an EVI file will be between 1% and 30% of the size of the original data file. Some Echoview operations, such as scrolling to the end of a large echogram, are substantially faster when EVI files are available.
You may safely delete EVI files at any time when Echoview is not running. Echoview will recreate them as required.
EVI files are created in the same folder as the original data file, and always have the same name as the original data file (including the extension), with ".EVI" appended. For example, the EVI file for "RIVER.DT4" will the "RIVER.DT4.EVI".
When Echoview uses data files that are stored in read-only locations, for example CDs, Echoview will be unable to create EVI files. In this situation Echoview will still operate correctly, but at a slower speed.
The EVI file format is proprietary and will change as new features are added to Echoview. Echoview accommodates such changes by deleting and recreating an EVI file whose format is incompatible with the running version of Echoview. This may create problems if multiple copies of different versions of Echoview are run concurrently on the same data files. In this situation we recommend all users upgrade to the same version of Echoview.
Echoview does not create EVI files for:
- BI500 data files, as the files ending in "-Ping" file perform a similar role
- netCDF4 data files, as these already contain the indexing that is normally stored in EVI files