For many years I have been using data from the global network of superconducting gravimeters, and from the broadband seismometer networks. I calculate the vector tidal gravitational acceleration at the stations to calibrate the single axis superconducting gravimeters, and the three axis seismometers. Once calibrated, they can be used as nodes in an imaging network to place constraints on the gravitational positions of the sun, moon and earth. With the three axis instruments, it is possible to solve for precise positions and orientations of the instruments. This can be used for a type of "gravitational GPS", which, in principle, will work 24 hours a day, anywhere on earth, without an array of GPS satellites.
In recent years, I have been looking for low cost, sensitive, three axis accelerometers, and related instruments that are sensitive enough to detect earth tides. There are MEMS accelerometers (called "gravimeters" when they are sensitive enough to track earth tides, the sun moon signal), cold atom gravimeters, and other technologies now. Even with relatively high noise levels, they can be individually calibrated to track and then report on the positions of the sun and moon. The noise suppression systems used at the gravitational wave observatories can actually be used as sensitive detectors of changes in the local acceleration field correlated with the positions of sun, moon, and earth. A network of them is right near the point where Venus and Saturn can be tracked. Some of the MEMS designers are aiming at cell phone markets, so there is potential for using millions of cell phone "gravimeter grade" accelerometers as a virtual telescope for imaging.
However, two things happened in the last couple of years that changed my direction. First, the gravitational wave signal and electromagnetic signals from the collision of two neutron stars in Aug of 2017 (labeled GW170817) show that gravity and electromagnetism propagate at exactly the same speed. One of the reasons I set about calibrating the gravimeter networks on earth was to measure the speed of gravity. Now that is not necessary, since the only way they can have the same speed, is if gravity and electromagnetism share the same potential. There are several things that can be checked. The second thing that happened is that the broadband seismometer networks are now sensitive enough to detect the direct gravitational signal from earthquakes. It propagates at the speed of light/gravity and can just register at the stations. Adapting that to various kinds of earthquake early warning systems will take a lot of effort, but at least it indicates what might be possible.
In order to design a purpose-built detector for propagating acceleration fields ("gravity" and "acceleration" are the same thing, but "gravity" is misused a lot), I have been investigating high sampling rate, three axis gravimeters. Individual calibration and massive oversampling is expected during development. But once the basics are down, FPGA and the sensor industries can probably field low cost, reliable devices.
The current global lightning mapping, and lightning imaging technologies rely on high sampling rate electromagnetic field sensors. The calculations are done in electromagnetic units, but the output is a 3D video of lightning strokes. More particularly, it is a 3D video of the source events that created the "electromagnetic" signals.
All of the "time of flight" imaging methods work for gravitational signals as well. These are not gravitational waves like the ones LIGO uses, but rather the result of changes in the gravitational potential which propagate when mass is moved, at the speed of gravity/light. The sensitivity requirements are such that only a few things can be imaged with current technologies. That can be offset with many low cost gravimeters, and with some expensive purpose built detectors.
My question for this community is this: How do I connect a gigasample per second ADC to the ADXL335 (analog 3 axis accelerometer)?
I need to run three of these for imaging. But one should allow me to check the instrument response, and see what signals it can pick up. If the internal sensors are not true measures of the field, I think, from doing similar things, I can correct that with extensive calibration. I am retired now. It took me a year and a half to find a way to calibrate the superconducting gravimeters. It took another 6 months to go through every seismometer in use to find which ones can be used for this type of gravimetry.
My notes on these developments is at GravityNotes.Org. Many new things are happening, it is hard to list them, let alone explain it all.
As far as I can determine, gravity and electromagnetism use the same underlying potential. The laser vacuum experiments are testing how mass is formed from the vacuum using intense lasers. New studies on particle-antiparticle stable states are changing our ideas of matter, and that is changing how we see gravity signals being generated, and then detected. My optimistic view is that anything you can do with electromagnetism you can also do with gravity. In simple terms, gravity is just an a part of the electromagnetic field. And the gravitational potential is what electromagnetism uses for propagating signals.
Sorry to write so much. I think there might be some good people in this group who can pick up these ideas and make quick progress. I have no vested interest in doing this all myself. Arrays of high sampling rate gravimeters require high speed correlators to acquire and process the signals to produce images of the interior of the earth, the oceans and atmosphere. I just turned 70, so I won't be around to see it all. But these are pretty exciting times.