Abstract: Shipboard gravity data are currently recorded with one shipboard gravity meter. Gravity data are tied to the international gravity datum when the boat docks about every 30 days. The accuracy of these data is about 0.5 milligals and not sufficiently accurate for detailed quantitative interpretation. It is possible to increase the accuracy of shipboard gravity data twofold by using the procedure we have described. A stable boat with precision navigation and water depth soundings is necessary. Two gravity meters are calibrated to read the same values and times. These are placed near the center of the boat with one meter facing forward and one facing backward for plus and minus cross coupling, or simultaneous accelerations in different directions. Integration of the gravity recordings cancels random noise. This innovation increases the accuracy to 0.35 milligals. Shipboard gravity data are tied to a coarser grid of still gravity readings tied to the international gravity datum at land locations.