The jamming of a GPS signal being transmitted to an unmanned aircraft system (UAS) could interrupt the command and control of UAS operations. In a GPS jamming scenario, the UAS could potentially lose its ability to determine its location, altitude, and the direction in which it is traveling.
Low cost devices that jam GPS signals are prevalent. According to one industry expert, GPS jamming would become a larger problem if GPS is the only method for navigating a UAS. This problem can be mitigated by having a second or redundant navigation system onboard the UAS that is not reliant on GPS, which is the case with larger UAS typically operated by DOD and DHS.
Encrypting civil GPS signals could make it more difficult to "spoof" or counterfeit a GPS signal that could interfere with the navigation of a UAS. Non-military GPS signals, unlike military GPS signals, are not encrypted and transparency and predictability make them vulnerable to being counterfeited, or spoofed. In a GPS-spoofing scenario, the GPS signal going from the ground control station to the UAS is first counterfeited and then overpowered. Once the authentic (original) GPS signal is overpowered, the UAS is partially under the control of the "spoofer."