I was researching GPS receivers for an high altitude balloon and most receivers stop working at more than 18km OR at 500m/s. Some manufacturers misinterpreted

I was researching GPS receivers for an high altitude balloon and most receivers stop working at more than 18km OR at 500m/s. Some manufacturers misinterpreted the restriction. Instead of OR it should be AND. If you look around high altitude balloon forums, they usually maintain a list of good gps chips(stop working at 500m/s AND 18km instead of 500m/s OR 18km).