Gravity instruments: Past, present, future

Geophysicists and geodesists have traditionally demanded high levels of accuracy from gravity sensors to make notoriously difficult measurements of extremely small differences in the earth’s gravity field. The earth’s gravity field ranges from about 983 000 mGal at the poles to about 978 000 mGal at the equator, yet we demand accuracies in the range of less than 1 mGal for typical surface-measured exploration targets. This means resolution of 1 part per million compared with the earth’s gravitational field.