My friends are running a company called FOAM Space that has also put a lot of research into 3D terrestrial-base positioning [1]. Their system, though, can also make "claims" about the position, which is a cryptographic proof that the object that created the claim was at location X at time Y. So, not only you can find where you are but you can also you prove to others that you are there. They use unregulated LoRa bandwidths to operate.

[1] https://foam.space/

EDIT: typos