# CUAV C-RTK
The CUAV C-RTK GPS receiver (opens new window) is an RTK GPS module for the mass market. A complete RTK system consists of at least two C-RTK modules (one for the base station and the others for the aircraft). Using RTK, PX4 can get its position with centimetre-level accuracy, which is much more accurate than can be provided by a normal GPS.
# Purchase
# Configuration
RTK setup and use on PX4 via QGroundControl is largely plug and play (see RTK GPS for more information).
# Wiring and Connections
C-RTK GPS comes with a cable that terminates in a 6-pin connector and 4-pin connector that are compatible with Pixhack v3 (opens new window). The 6-pin connector provides the interface for RTK GPS, and should be connected to the flight controller's GPS port. The 4-pin connector is an m8n (standard) GPS interface that is intended for (optional) use as a second GPS.
TIP
At time of writing PX4 does not yet fully support a second GPS. The 4-pin port need not be connected.
The cables/connectors may need to be modified in order to connect to other flight controller boards. The pin mappings for Pixhawk 3 Pro and Pixracer are shown below.
# Pinout
The C-RTK GPS pinout is provided below. This can be used to help modify the connector for other autopilot boards.
| pin | C-RTK GPS 6P | pin | Pixhawk 3 Pro GPS | C-RTK GPS 4P |
|---|---|---|---|---|
| 1 | SDA | 1 | VCC | |
| 2 | SCL | 2 | GPS_TX | |
| 3 | GPS_RX | 3 | GPS_RX | GPS_RX |
| 4 | GPS_TX | 4 | SCL | GPS_TX |
| 5 | VCC_5V | 5 | SDA | VCC_5v |
| 6 | GND | 6 | GND | GND |