Precise positioning is vital for UAVs to accomplish complicated missions successfully in various environments. However, in practice, it is challenging for commercial small UAVs to achieve high accuracy positioning. One of the reasons is that most of high-performance navigation equipment is heavy and high-priced. One solution to this issue is the use of Local-Area Differential GNSS (LADGNSS) which broadcasts differential corrections to UAVs in the vicinity of the LADGNSS ground station. By using the differential corrections, the UAVs can carry out their missions with sub-meter level accuracy. In this research, in order to verify that the navigation performance improves when the UAVs employ the LADGNSS corrections, flight tests are carried out with octo-copters. These octo-copters are equipped with commercial controllers employing on-board MEMS sensors, NovAtel receivers, and communication modules. Overall, two types of flight tests are conducted: altitude holding of multiple UAVs, and precise landing. In the first flight test, relative vertical errors were estimated while the UAVs held the same altitude. In the second flight test, the coordinates of the landing points were collected after the UAVs landed on designated positions,. These data are statistically analyzed to assess the improvement in the landing accuracy when LADGNSS is applied. Also, in this paper, the entire system configuration is demonstrated in detail including the hardware configuration of the UAVs and description of the KAIST LADGNSS test-bed.

Keywords: LADGNSS, UAVs, flight test