u-blox ZED-F9P

The ZED-F9P from u-blox of Switzerland is a high-precision multi-band GNSS module with integrated RTK in an LGA package of 17 x 22 x 2.4 mm. It is not assigned to a drone class but is widely used in RTK units for drones: it sits among others in the Holybro H-RTK ZED-F9P, the CUAV C-RTK 9Ps, the ARK RTK GPS and the Drotek boards DP0601 and SIRIUS.

The chip has 184 channels and handles GPS, GLONASS, Galileo, BeiDou, QZSS, SBAS and NavIC. There are two band variants: the -02B, -04B and -05B versions use L1 and L2 (L1C/A, L2C, L1OF, L2OF, E1B/C, E5b, B1I, B2I), the -15B version uses L1 and L5 (L1C/A, L5, E1B/C, E5a, B1I, B2a and NavIC L5). Moving base, that is heading from two receivers, is offered only by the L1/L2 version. For RTK u-blox states 0.01 m + 1 ppm as CEP, that is 1 cm at a radius containing half of the measurements, with a convergence time under 10 s. The rate is 20 Hz; it can limit the number of constellations used at once. Connection is through two UARTs, USB, SPI and I2C (DDC); NMEA, UBX, RTCM 3.4 and SPARTN 2.0.1 are spoken.

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. RTK improves that position but replaces none of the duties. Correction data come from your own base, a radio link or an NTRIP service; SPARTN enables PPP-RTK through providers.

When choosing a product with this chip, the band variant counts: L1/L2 for moving base, L1/L5 for the newer signal. The centimetre class depends on antenna, ground plane and distance from transmitters, not only on the chip. Upkeep includes the chip's firmware, because it sets rates and messages.