I have spent the last year going over possible technologies and methods.  My criteria for the gravitational imaging network is

Three axes : so that each sensor can determine direction. Each axis of the signal is very precise. Fitting a one dimensional signal is ambiguous.  Fitting three orthogonal axes signals at once is very precise.  A three axis gravimeter can be as precise or more precise than a GPS station.  And you can solve for the orientation of the sensor.  We are not to where someone walking around can use it like a gravitational compass, but I think in the future that will be possible.  I started out just trying to track the sun an moon precisely. But in the last 17 years I have learned a few things.

High Sampling Rate:  So that arrays of sensors can correlate and solve for direction of the source.  Higher data rates mean more samples and data to characterize and study the source.  Higher rates over time mean a wide range of single pixel and super-resolution and correlation techniques can be applied.

Arrays:  From the beginning, I knew that the  current sensors are crude, and the gravitational signals are mixed in with magnetic, thermal, seismic, acoustic, and many sources of noise. But even though the signals move at the speed of light and gravity at a million samples per second, each microsecond sample is 299.8 meters. At a Giga samples per second that is 0.2998 meters or 29.98 centimeters.  

I spent much of the last couple of decades trying to find sensors that are sensitive to gravity, to magnetic and electromagnetic fields. My intention is to then correlate to global "magnetic" and "electric" and "acoustic" and "gravitational" and "thermal" sensor networks and then use statistical methods to sort out and calibrate all the signals.  Most of the noise is a mixture of radiation field (particularly thermal radiation), low frequency magnetic and electric, and many many natural and man made sources of electromagnetic noise.  The movements of air (remember we are looking at things at Msps and Gsps so all the acoustic and ultrasonic events and air movements are there in principle.

An earthquake is not an instantaneous explosion. Rather it is the movement of mass in one area that causes movement to spread out in a pretty well known, and "model-able" way. The surface waves are fairly obvious. Cubic voxels that only held air get filled with soil and rock and water. Later they get filled with air again.  Those seismic surface waves and interior wave are tracked precisely by thousands of sensitive and daily more integrated sensor networks. So the gravitational potential changes with time can be calculated.  That travels out at the speed of light, and the signal gradient (the acceleration field) at sensor locations is reliable and can be used to learn more about the mass distributions, speeds and volumes and locations.

The electron is a wonderful tool. It has electric charge so it responds to electric fields, It has magnetic moment so that it responds to changing magnetic fields and gradients. It has mass, so it responds to change in the gravitational potential and its gradients.  I have come to treat the gravitational and electromagnetic fields as one field. And I can use the properties and behaviors of electrons to sort out and quantify the contributions from each field to motions and orientations of single electrons, and groups of electrons. The atoms and molecules and particles and gluons and states of matter and the vacuum are there as a backdrop. 

I am spending more and more time looking at and organizing information related to "single electron" and "single photon" devices. These seem rather wonderful that people are getting down to that level of precisions. But I finally understood where to put the "magnetic flux quantum".

If you ask, what is the energy of a photon whose frequency is 1 Hertz, in electron Volts, you get your answer by multiplying by Planck's Constant, then dividing by the elementary charge. That is 6.62607015 x 10^-34 Joules/Hertz time 1 Hertz divided by 1.602176634  x 10^-19 Joules/ElectronVolt to get 2 times 2.067833848  x 10^-15 ElectronVolts.  

I wrote it this way because h/e is the energy of a 1 Hertz photon. And that is twice the numeric value for the magnetic flux quantum. So you can think of a 1 Hertz photon as a pair of bound magnetic flux quantums at least in terms of the energy the photon carries. Now this is not perfect, but a good way for me to thing about the energy density and flows associated with the gravitational field and electromagnetic field.  I like the magnetic flux quantum as a unit of energy, because most of the sensors for gravity are down in the nano, pico, femto, atto and smaller scales.  nano meters per second squared for sun and moon signals on the earths surface.  Pico and femto meters per second squared for earthquakes and tracking planets. and find details of parcels of air or currents and waves in oceans.  

I am probably going to run out of space on Hackaday.io   It is hard for me to work where I control the colors and layouts.