Hmmm, pass the salt and call me a skeptic. I've never read this anywhere. PLS images look much nicer on my Ultra 102sv which has 1280 x 800 pixels, compared to 800 x 400 of my 93sv UHD, in my personal experience.
If the image itself is created in the GLS10, as your post seems to assert, how are the different display modes (with varying aspect ratio) VGA, XVGA, FHD of the various chartplotter series handled? I have not read anything anywhere that suggests that the GLS10 module has a fixed resolution at a low standard, or what that resolution actually is. I'd like to see anything on the subject you have that is from Garmin. IMO YMMV
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