GPS Velocity and update rate

[BarrelRoll]

Does a GPS unit provides a direct velocity information?
As far as I understand in most cases the velocity is calculated using two consequent position measurements.

Another question is there a commercially available GPS module with 10+ Hz update rate?

[Jack Crossfire]

Horizontal GPS velocity is based on doppler shift and is pretty good. Vertical GPS velocity is not calculated. Accuracy declines as update rate increases over 1Hz, but units can fake higher update rates by delaying and interpolating. Owners who spend the $120 on higher update rates swear they're calculating fully independent, non interpolated, non delayed readings of course.