GitHub - sparkfun/SparkFun_RTK_Firmware: Centimeter precision GPS/GNSS using L1/L2 signals broadcast over Bluetooth SPP (using the ESP32) in an easy to use enclosure.
SparkFun GPS-RTK2 Board | 3D CAD Model Library | GrabCAD
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GPS-RTK2 Hookup Guide - learn.sparkfun.com
SparkFun GPS-RTK Dead Reckoning pHAT for Raspberry Pi | Elektor