Tech Chat | Understanding The Communication Interfaces in RTK GNSS Receivers

In our earlier blog, we explored the overall structure of RTK GNSS receivers and mentioned the mainboard as one of the core components. The mainboard itself integrates various elements, such as the GNSS module, system platform, functional modules, and communication systems. In this blog, we’ll focus specifically on the communication systems built into the mainboard. Other parts will be discussed in future posts in this series.

Modern RTK receivers are designed to serve different field applications—from surveying and mapping to agriculture and construction. To support diverse working scenarios, these receivers may be equipped with different communication options. While not every model includes all the types mentioned below, this blog summarizes the most commonly used communication interfaces seen across various GNSS receivers.

1. GSM/4G

4G modules allow the RTK receiver to connect to CORS (Continuously Operating Reference Station) server over the internet. This enables real-time corrections uploading or receiving, especially useful in wide-area coverage and mobile mapping. The internal 4G is

Use case: The internal 4G/GSM is more commonly used for internal GSM base mode.

2. Wi-Fi

Wi-Fi connectivity enables wireless data transfer and configuration between the receiver and external devices such as mobile phones, computers, or controllers. Most RTK receivers' built-in web page can be accessed via WiFi. 

For RTK receivers with camera, the WiFi is used for image/video data transmission due to the large data amount.

Use case: Device configuration, firmware upgrade, static data download, AR image transmission.

3. UHF Radio

UHF communication is one of the most traditional methods for base-to-rover RTK data transfer. It supports different protocols based on compatibility:

• Transparent: Raw data passthrough

• TrimTalk, Satel, etc., : Various standard and proprietary protocols ensure cross-brand compatibility

• LoRa: A low-power, long-range radio protocol also widely used in GNSS applications

Use case: RTK corrections transmission (typically 2–15 km in internal radio mode, varying via different environments), ideal for remote areas with no 4G signal.

4. Bluetooth (BT)

Bluetooth allows for close-range wireless communication between the GNSS receiver and external smart devices (controllers, smart phones). Most receivers support:

• BT 2.0 for classic Bluetooth

• BLE (Bluetooth Low Energy) for improved efficiency and power-saving

Backward compatibility with BT 4.0 ensures broader device support.

Use case: Wireless connection to data collectors, controllers, or mobile apps.

5. Serial Ports

Serial communication is crucial for hardware-based data exchange and external system integration:

• RS232: Typically used for connecting external radios or computer configurations.

• RS485: Used for robust communication with devices like meteorological sensors or external modules like gas analyzers or split machines.

• CAN*(For GNSS Sensors): Suitable for automotive or agricultural equipment requiring fast and reliable data exchange.

Use case: System integration with external equipment.

6. USB

USB interfaces support data import/export, firmware upgrades, power charge, or PC-based configuration. It also powers easy plug-and-play connectivity with computers or field controllers.

Use case: Field data transfer, receiver configuration, charging, or firmware updates.

7. Regulatory Certifications

Different countries and regions impose varying certification requirements on communication systems used in GNSS receivers to ensure safe and compliant operation. Common certifications include CE, FCC, KC, NTBC, and NCC, which represent approval for communication modules across different markets.

By offering a wide range of communication interfaces, modern RTK GNSS receivers can adapt to various workflows and field scenarios. Selecting the appropriate communication setup—depending on the receiver model and intended use—is essential for maximizing performance and reliability in real-world applications.