 Software Glitch in the Garmin GSD22 Sounder
This is a suggestion that will hopefully find its way to someone who knows the right people at Garmin. I use a Garmin 3010C and recently added the GSD-22 Sounder with an Airmar B260 1kw transducer. Everything works fine, but there is a major software glitch in the way the Garmin depth sounder functions when used in the auto zoom mode.
I also have a Raymarine L760 sounder on the boat and use the zoom feature extensively when looking for spots to try when bottom fishing. On the L760, the zoomed display is very stable when in the auto mode, it only resets the placement of the zoomed range on the display when the edge of the zoomed bottom echo reaches the upper or lower limits of the screen display.
When in the auto zoom mode, the Garmin display is very unstable…it jitters constantly and rapidly, making it almost impossible to get a good look at the bottom features. The jitter frequency appears to coincide with the refresh frequency of the display. This would imply that the Garmin software is designed to try and hold the edge of the zoomed bottom echo at a constant spot on the screen. When you are bouncing around in 3-4’ chop, the auto zoom bottom display will jitter just as much, making it virtually unusable, and forcing the user to go to the manual zoom mode in order to stabilize the screen display. The drawback to this mode of operation is you must manually reset the zoom range a lot when watching uneven bottom structure.
It would seem that this is a flaw in the design of the software, something that could be easily fixed in one of the Garmin software upgrades.
There are a couple of ways to reduce the jitter. First, you could redo the software to mimic the Raymarine style of locking the zoom range until the edge of the zoomed bottom echo starts to leave the screen. At the very least you could apply the same principle to locking the zoom range until the edge of the bottom echo moves at least XX% of the screen range. The other option would be to slow down the reset frequency of the zoom range (not the display itself, just the range that is displayed). About one range adjustment per second would reduce the jitter to an acceptable level.
I could not find a way to ship this suggestion to Garmin on their website, so hopefully someone with the right contacts at Garmin could pass this along.
| 
