Measuring postglacial rebound with GPS and absolute gravity

We compare vertical rates of deformation derived
from continuous Global Positioning System (GPS) observations
and episodic measurements of absolute gravity.
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 are signi cantly
more precise than the gravity rates, primarily because of
the denser temporal spacing provided by continuous GPS
tracking. We conclude that continuous GPS observations
are more cost e cient and provide more precise estimates of
vertical deformation rates than campaign style gravity observations
where systematic errors are di cult to quantify.