This is from a post last year when I was testing some of this......
OK, I did some testing to see how far I could go with this......
If you rename a snapshot's waypoint it DOES NOT rename the snapshot image. This we know. And the snapshot preview will still come up when you move cursor over the waypoint, even though the waypoint name and snapshot name are not the same. Hit the info button and View Snapshot and the full size shapshot comes up as well.
So the snapshot is not being reference by name, its being done by the GPS coordinate in the .DAT file of the Snapshot. I performed a test to confirm this by switching the headers of two .DAT files and they both reversed the snapshots and preview images. Confirmed.
Also, you CAN rename a snapshot and have it display the preview image and snapshot correctly, just as long as you rename both the .PNG and .DAT to the same name. However, when viewing it on the RECORD/SNAPSHOT screen, the file name would not be correct. This is because the gps info, date, and displayed file name on that screen is read from inside the .DAT file. In order to change this, you would need a hex editor program.
I even renamed one shapshots .DAT and .PNG files to Shipwreck123456789 to see if name length mattered and it worked fine when viewed on the unit. However, the internal name length is limited to 10 Characters.
So, in conclusion. It is OK to rename a Snapshot Waypoint and not rename the snapshot. And it is OK to rename a Snapshot, just as long as you rename both the .DAT and .PNG file.
Robert