I imagine they could used for navigation, too once accurate gravity maps are established.
gravimetric navigation is used by the Navy on submarines, it’s accuracy and the gravity vector maps are all highly classified but yes it not only is possible it is used on a regular basis presently by our boomer subs.
the theoretical accuracy at part per billion in G is tens of meters if the maps are also made at part per billion resolution. Think Tercom navigation but instead of topography vectors as the truth sources gravity vectors are used with comparable accuracy as a note tercom on our cruise missiles is good to about 200 meters cep. One of my degrees is in Geospatial sciences we have been looking at using gravimetrics in the petroleum industry via airborne sources to do reservoir depletion geocellular gridding.
“I imagine they could used for navigation, too once accurate gravity maps are established.”
A replacement for when the magnetic poles go berserk?