You can get a Part 5 experimental license, although a likely condition of getting such a license would be taking steps to ensure that your work doesn't interfer

You can get a Part 5 experimental license, although a likely condition of getting such a license would be taking steps to ensure that your work doesn't interfere with devices outside of a small designated test area. Alternatively, you can do all the GPS experimentation you want inside of a shielded chamber without asking permission from anyone.