Measuring gravity to improve coastal monitoring

Science: How high is up? The US government has launched a 10-year, $38 million research project called Gravity for the Redefinition of the American Vertical Datum (GRAV-D) to answer that question in hopes of improving its management of coastal regions and reducing the damage from severe storms and rising sea levels.

The key instrument is an airborne gravimeter coupled with GPS. Placed inside the National Oceanic and Atmospheric Administration's Cessna Citation II jet, the gravimeters will measure the acceleration of gravity at the same time that GPS instruments aboard NASA's Gravity Recovery and Climate Experiment satellite measure the plane's vertical acceleration. Thus, equipped researchers can produce large-scale regional land and sea surveys without the inconsistencies of leveling, says Vicki Childers, project manager for GRAV-D.