The speed reading is ok on the N950 but is not on the N900.

Basically, the QtMobility API dictates that the speed is provided in m/s units - but this is inconsistant with the actual speed reading which is about ~3 times higher then expected.

I have used this site and it approximate that the provided speed units are actually in ft/s. :O

Update:
Then I found this link that sorts things out http://developer.qt.nokia.com/forums/viewthread/1804