u-blox NEO-M9N

The NEO-M9N from u-blox of Switzerland is an L1 GNSS module with metre accuracy, four concurrently received satellite systems and detection of interference and spoofing. It is not assigned to a drone class but is the widespread basis of GPS units for drones: it sits in the Holybro M9N GPS, the CUAV NEO 3 Pro and the ARK GPS.

The chip has 92 channels and handles GPS (L1C/A), GLONASS (L1OF), Galileo (E1B/C), BeiDou (B1I), QZSS and SBAS in the L1 band. It does not offer RTK. u-blox states 1.5 m CEP with SBAS and 2.0 m CEP without SBAS, the radius containing half of the measurements; SBAS is a correction service via satellite. The rate is 25 Hz, according to u-blox also with four systems at once. Connection is through UART, USB, SPI and I2C; NMEA 4.10, UBX and RTCM 3.3 are spoken. The chip weighs 1.0 g.

Jamming is the deliberate drowning of satellite signals with a jammer, spoofing the faking of false signals. Detecting both allows the flight system to fall back on other sources or to land. Operating a jammer is reserved for authorities in Germany and Poland. A chip is not an aircraft: the duties of the EU drone regulation arise at the aircraft, where geo-awareness and remote identification (from class C1) rest on the GNSS position. Metre class is enough for that.

For selection the build of the finished product decides, not the chip alone: antenna, ground plane and distance from transmitters determine the accuracy, and the compass in the module needs a mast. Anyone who will later need centimetre accuracy chooses an RTK module straight away, because the M9N cannot be upgraded. Upkeep includes the chip's firmware.