Here are images. First is mio & then navigon. Screen resolutions are different. Navigon is 480 X 272. Mio is 800 X 480.
You can see ATZ is stretched widthways
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Here its definitely circular!
Sorry re picture quality. But you can see the difference.
Dont know if there is any tweak that can be done. Also its easy to live with the effect.
400NIT screen of navigon is also quite apparent.
David