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.
EDIT: typos