GNSS & GPS
Meter-level L1 modules and centimeter-level multi-band RTK kits are different classes of receiver. Pick the accuracy class and required constellations first, then the interface.
Adafruit Ultimate GPS (PA1616S/PA1616D), NEO-6M and NEO-M9N u-blox breakouts, Gravity GNSS BeiDou boards with I2C/UART, and 4G or LoRa RTK kits — accuracy and constellation requirements split them.
- Adafruit Ultimate GPS (PA1616S, and PA1616D with GLONASS), the GY-NEO6MV2, and the NEO-7M-C UART module are classic meter-level L1 receivers; SparkFun's NEO-M9N Qwiic breakouts add multi-constellation tracking and I2C.
- DFRobot's GNSS-RTK kits reach 5 cm + 1 ppm by pulling RTCM corrections over 4G NTRIP or a LoRa link, and they pair with multi-frequency L1/L5 active antennas, not a 9 mm passive patch.
- Gravity GNSS GPS BeiDou modules expose both I2C and UART (one variant adds an RTC); the L76K (GPS, BDS, QZSS) and the M5Stack AT6668 GPS/BDS unit cover compact builds.
- Tracker combos such as the A9G, LoNet/FONA 808, and SIM7070G put GNSS and cellular on one module — right for asset tracking, overkill for a stationary timebase.
