Sorry for the long delay in getting back with you. I was at the Treasure Expo over in Myrtle Beach and had my hands full.
The ping rate is only changeable in snapshotview and recording view. Now the explanation is a little complicated but the final answer is not. The ping rate is the amount of time the system will listen for sonar returns. Sound travels through salt water at around 1500m/s and through and in fresh water at around 1497m/s. Now there are many veriables to those numbers, salinity, depth, and temperature. If the range setting in short say 50' the ping rate will be faster than at a setting of 200'.
This can be usefull in cutting down recording size, but with larger cards available I think its a mute point.
If you set the ping rate manually, the system may be not be listening long enough for the ping and the data may be incomplete in the recording. It will cause the ping data length (number of bytes recorded in each ping) to vary and you will end up with jagged edges on the image during playback.
Now, what is the optimum ping rate for the range setting. Hmmmm! The answer is, AUTO.
Good Luck,
Robert