He is known for his invention of a precise method for measuring gravity.
Thanks to his invention, it became possible to measure gravity at sea, which led him to the discovery of gravity anomalies above the ocean floor.
Now it became possible to measure gravity more accurately.
Vening Meinesz started with measuring gravity all over the Netherlands, for which a network of 51 monitoring stations was created.
Now measuring gravity at sea had become possible.
Modern hydrometers usually measure specific gravity but different scales were (and sometimes still are) used in certain industries.
By measuring gravity they were able to detect what looks like two clouds of dark matter, with a cloud of normal matter (hot gas) in between them.
One commercially available unit claims the instrument is capable of measuring specific gravity with an accuracy of 0.005 SG units.
The Baumé scale measures specific gravity or relative density.
If you are measuring gravity on the ocean from a moving ship here are several other effects that come into play.