Which system is NOT categorized as a GNSS?

The correct answer is the system that does not fall under the classification of Global Navigation Satellite Systems (GNSS). GPS (Global Positioning System), GLONASS (Global Navigation Satellite System), and Galileo are all satellite-based navigation systems that provide global positioning capabilities utilizing satellite signals to determine accurate locations on the Earth's surface.

In contrast, VOR (VHF Omnidirectional Range) is a type of radio navigation system for aircraft, providing guidance through ground-based stations rather than satellites. It transmits signals that pilots can use to determine their position relative to the VOR station and navigate accordingly. Since VOR does not rely on satellite technology for positioning, it is not categorized as a GNSS. This distinction highlights that GNSS systems operate using satellite constellations, while VOR is strictly a terrestrial navigation aid.