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Most drones are equipped with GPS but now the latest drones have dual Global Navigation Satellite Systems (GNSS) [13] such as GPS [14] and GLONASS [3] (Global Orbiting Navigation Satellite System, Russian). Drones can fly in both non-satellite mode and GNSS mode. For example, DJI drones can fly in P-Mode (GPS and GLONASS) or ATTI mode, which don’t use GPS. Highly accurate drone navigation is important while flying, as it has immense importance in drone applications such as surveying the landscape, SAR (Search and Rescue) missions, and creating 3D maps.

When the quadcopter is switched on its navigation satellite searches and detects GNSS satellite. High-end GNSS systems use satellite Constellation Technology. A satellite constellation is a group of satellites working together in near proximity and sync with one another giving coordinated coverage. This is done in such a way that these satellites overlap an area and is well in coverage. Here, pass or coverage is referred to as the period in which a satellite is visible above the local horizon.