About the etymology:
Is it not from Ancient Greek χάρτης (khártēs) as the word قرطاس?
There's always the possibility of coincidence. But I suppose there is a relation, particularly since there is a by-form خارِطة(ḵāriṭa). However, I don't know what kind of relation. The Greek word seems to be native. If so, maybe خريطة, خارطة was borrowed through a different path.