Very cool to see how it is done now! Thanks for sharing! I've done this kind of visualizations back in 2009 (i think I was still on Mathematica 6!) with some GPS data I recorded myself in a flight. It sure is now quite a bit easier to work with gps data and maps and so on!
Extract[img, Position[img, #]]
Why not use Cases or even FirstCase ? Grounds speeds above Mach 1 do indeed occur because of ~200km/h tailwinds! From the PDF 625 knots seems to be the limit, 697 might also contain measurement errors?