When enabled (checked off) it records the real-time data into a .gnssbin file, which can be replayed on the test set later on, to replicate the same results.
When Save Replay Files is enabled 
in the MTTplus SkyView™ GPS/GNSS antenna reception quality pattern verification tool, it records the received real-time data into a .gnssbin log file, which can be replayed in the test set later on, to replicate the same results (e.g., reporting, troubleshooting, training, demos, etc.).
However, keep in mind that this recording is considered optional, because it requires large amounts of memory. The total file size will depend on total test time, number of constellations, bands and satellites in view being tracked.
If enabled, the test set will start recording the raw information received from all satellites in view, while the SkyView test is running. Once the test is stopped and the result files transferred to an external USB memory stick, users can go to the Replay tab and view all the test files available in the external memory stick's \gnss folder.
Select the desired test result folder, select the .gnssbin file and tap on the Start button to start playing the recorded data back.
The log file can be replayed at different speeds, from 1x to 60x. Select 60x and tap on OK. At this rate, a 72-hour test replay would take about 1.2 hours to complete.
During the replay, a red Replaying label is displayed on the user interface, to prevent confusing it with a real-time test. Users can still interact with the application, as if the test was currently running, to show or hide GNSS constellations, look at events as they happened, etc.
Users can stop the replay session at any time, by going to the Replay tab and tapping on the Stop button.