General guidelines for 512 Hz wireless data transfer

Hi, I'm building a probe that needs to communicate through the ground, all the usual frequencies would not reach any lower than a few inches to about 1 ft in dry ground. I'm usually between 3 to 6 ft deep sometimes in clay.
I'm already generating signal to locate the probe and receive it fine at 512 Hz and 32.8 kHz, stepping this project further I want the probe to send pressure and a few Analog reading to a receiver above the ground.
So far I'm using Arduino Micro, Fet driver and coil antenna.
Beeing a total noob in data transfer, I'm looking for an existing protocol that can be useable at a extremely low frequency. I will need to build both antennas and probably some analog to digital converter, filter, etc
So if someone have seen a project like this, know good reading for getting me started I would appreciate some help

Thanks !

How about induction?
That's what cavers use, I believe

Hi, it's based on the induction cable locating principles, usually we put a current in a cable and pick up the induction then mark on the ground, a sonde is a smaller device that we insert on a conduit with a coil antenna. We are able to find the sonde with it's ocillating magnetic field.
Since I can pick up the 512 Hz sine, I was thinking of modulating or chopping the signal to send more precise data on the surface receiver.