Measuring postglacial rebound with GPS and absolute gravity

We compare vertical rates of deformation derived from continuous Global Pos itioning System (GPS) observations and episodic measurements of absolute gr avity. We concentrate on 4 sites in a region of North America experiencing postglacial rebound. The rates of uplift from gravity and GPS agree within one standard deviation for all sites. The GPS vertical deformation rates ar e significantly more precise than the gravity rates, primarily because of t he denser temporal spacing provided by continuous GPS tracking. We conclude that continuous GPS observations are more cost efficient and provide more precise estimates of vertical deformation rates than campaign style gravity observations where systematic errors are difficult to quantify.