GNSS modules for drones

GNSS modules determine the drone's position and velocity from satellite signals and often include a compass. Without RTK their accuracy is at metre level, which is sufficient for position hold, return-to-home and navigation.

Chipset

GNSS receiver chip, such as u-blox ZED-F9P, X20 or Septentrio mosaic. The chipset determines bands, constellations and achievable accuracy; the board around it determines antenna, compass and connectors.

Frequency bands

Signal bands used, for example L1 only or additionally L2, L5 and E5a. Multi-band receivers correct ionospheric delay errors and reach RTK solutions faster and more reliably.

Horizontal accuracy (cm)

Horizontal position accuracy without RTK in centimetres, usually as CEP (radius containing half of the fixes). Whether it was measured with or without SBAS is stated in the accuracy note.

Accuracy note

The manufacturer's original statement including the measure (CEP or RMS), the ppm term and conditions. Where no figure is given, accuracy is not documented and should not be ranked.

Weight (g)

Mass of the part in grams as stated by the manufacturer. Check whether cables, mounts or accessories are included, as manufacturers report this differently.

Compass

Built-in magnetometer, such as RM3100, IST8310 or BMM150. A compass in the GNSS module sits far from power cables and motors and therefore measures with less interference.

RTK capable

True when the receiver processes RTK corrections from a base station or a correction service. Without RTK, accuracy is at metre level; with RTK, at centimetre level.

Interfaces

Connections to the flight controller, such as UART, I2C, USB or DroneCAN. CAN modules work with longer cables and several devices on one bus.

Constellations

GNSS constellations received, such as GPS, Galileo, GLONASS, BeiDou, QZSS, NavIC, plus SBAS corrections. More constellations mean more visible satellites, which helps in urban canyons and under trees.

Update rate (Hz)

How many times per second the receiver outputs a new position. Higher rates help with fast flight and precise control; the maximum often applies only to a subset of constellations.

Modern single-band modules (u-blox M9 and M10 in the data) receive several constellations at once and are light and power-efficient. A built-in compass should be mounted far from power cables, which is why GNSS modules usually sit on a mast. For PX4 and ArduPilot, DroneCAN modules simplify wiring, while FPV boards mostly use UART. Anyone who will need centimetre accuracy later should choose an RTK module straight away. Accuracy is usually stated as CEP, sometimes with and sometimes without SBAS.

Accuracies are stated as CEP or RMS depending on the manufacturer and, for RTK, exclude the distance-dependent ppm term. Values are only shown together with the accuracy note and are not ranked without it.

Is a GNSS module without RTK enough for surveying?

For simple overview images yes, for survey-grade results no; those require RTK or ground control points.

What does SBAS do?

SBAS broadcasts corrections via geostationary satellites (EGNOS in Europe) and improves accuracy without an own base station.

Why is the GNSS module often on a mast?

So that compass and antenna are disturbed as little as possible by the drone's power, motors and radio.