Simrad NSO Operation Manual page 24

The Photo overlay function is disabled as you zoom out beyond a certain level.
Photo transparency
The transparency sets the opaqueness of the photo overlay.
Navionics Fish'n Chip
NSO supports Navionics Fish'n Chip (US only). Fish'n Chip
provides high resolution bathymetric data.
Fish'n Chip data is standard on Navionics Platinum Plus cards.
If enabled, you may notice some other chart features
disappear and it may clutter the screen.
Using charts | 23