It isn't as hard as you might think. Most gravity-gradient measurements are differential. Common-mode accelerations can be substantially-rejected. Also, if yo

It isn't as hard as you might think. Most gravity-gradient measurements are differential. Common-mode accelerations can be substantially-rejected. Also, if you're in the precision-measurement game, navigationally-relevant signals can be much larger than the precision of modern instruments. People in the prospecting business sometimes fly gravity-gradiometers in airplanes.