Q: Discovering gravimetric station data, including location and measurement? I would like to refine an precision estimate of local gravity based upon current GPS position. Ideally, similar to the National Weather Service API, I would like to interrogate a server with a REST interface, providing location and accepting gravimetric data in return. If no such service is available, I would consider hosting mgal data and referencing its value by location, possibly with interpolation. 
Together with other natural measurements, this gravity data would be an input to a developing Android application. (No, I don't deem the device's native sensors sufficiently accurate for this; thus, I am seeking a benchmark reference.)

A: The United States National Geodetic Survey has been working on collecting widespread gravitmetric measurements, and publishing them for their GRAV-D campaign. The data in being collected for the next major vertical datum change in 2022.
