Voici la réponse de Remzibi .
About position , all depends of what mps are you using with what offset .
If it is google maps so the offset of GPS (GPS Datum) must be set to 220=WGS 1984 Global Definition
Then when we typing position in google - must be typed propertly
here is typical mistake of user http://www.rcgroups.com/forums/showpost.php?p=18357689&postcount=3307
and my answer with proper typing http://www.rcgroups.com/forums/showpost.php?p=18358015&postcount=3308
About the altitude , it is only GPS ability , OSD simply typ the value delivered by GPS .
Altitude is not a function of GPS it is implemented "by the way" .
Some more information about altitude errors is here https://sites.google.com/site/remzibiosd/2-remzibiosd/4-gps-module