Global navigation satellite system (GNSS) is the generic term for GPS that will be used in this section going forward. GNSS is used instead of GPS because there are multiple GNSS systems offered by the U.S., Russia, China, the EU, etc. GPS is the GNSS created and maintained by the United States government.
GNSS in combination with other sensors such as a barometer is the most popular means for a UAS to know where it is in the world. UAS conducting property inspections will be in close proximity to structures they are capturing, meaning position accuracy is critical. The U.S. GPS offers accuracy of roughly 3.5 meters per FAA real-world data but accuracy and the overall reliability can be improved with a variety of methods. One example is real-time kinematics (RTK) which can use a reference station to achieve centimeter level accuracy. Another example is one-chip, multi-GNSS receivers that increase reliability by combining the United States’ GPS and Russia’s GLONASS constellations.
GNSS signals are relatively high frequency and low power by the time they are received on the surface of the earth. This makes it very difficult to test UAS systems that use GNSS positioning inside a building and in many cases, even in close proximity to a building.
An outdoor net provides an ideal enclosure for testing GNSS technologies on UAS and the reliability of GNSS under different conditions. GNSS signals can easily pass through the net while the net ensures that a UAS equipped with an unproven or prototype GNSS does not become a runaway. Flight plans can be executed repetitively to verify that a particular GNSS solution is statistically reliable enough for daily operations in a residential neighborhood.