Designed and manufactured in Boulder, Colorado, USA, the SparkFun RTK Reference Station is the perfect solution for your high-precision geolocation, surveying, and time reference needs. For basic users, it is incredibly easy to set up a fixed location NTRIP server, enabling RTK for rovers and even as an NTP server for equipment synchronization and an astoundingly accurate time base.

RTK is short for Real Time Kinematics. A satellite positioning receiver capable of RTK takes in the normal signals from the Global Navigation Satellite Systems (GNSS) along with a correction data stream to achieve improved positional accuracy. GNSS includes satellites from GPS (USA), GLONASS (Russia), Beidou (China), Galileo (Europe), plus special additional satellites (e.g., SBAS and QZSS). On their own, these signals will deliver ~30cm positional accuracy. An RTK receiver takes in an additional Real Time Correction Message (RTCM) data stream and then calculates the device's location with 1cm accuracy in real-time. RTK works best when the correction data is generated locally; the 'Rover' receiver accuracy degrades as the distance (baseline) between it and the 'Base' generating the corrections increases. With just a few minutes of setup, the SparkFun Reference Station allows you to generate that correction data locally and share it via Ethernet!

Under the hood, the Reference Station is based on the ESP32-WROOM processor and u-blox ZED-F9P multi-band GNSS module. It runs the same open-source firmware as our other RTK products. The Reference Station has 10/100 Mbps Ethernet connectivity and it can be powered by Power-over-Ethernet (PoE). The microSD card is connected via a 4-bit SDIO interface, providing an order of magnitude improvement in read and write speed. Similarly, the u-blox ZED-F9P GNSS module is connected via a high-speed SPI interface, also providing an order of magnitude improvement in the GNSS data transfer speed. Want to log RAWX and SFRBX from all constellations at 20Hz? With this product, you can! We also included an ATECC608A crypto co-processor if you want to write your own firmware and use the Reference Station for crypto mining/space weather station applications or to secure/authenticate your GNSS data.

Need an affordable Network Time Protocol (NTP) time server for your Ethernet network? We've got you covered. The Reference Station can also act as an NTP server. Having your own NTP server allows the computers on your Ethernet network to achieve much closer clock synchronization. The Reference Station supports DHCP by default, but you can give it a fixed IP address if you want to. DNS, gateway, and subnet mask are all configurable too.

We've designed the Reference Station to be robust and lab friendly. Internally, all of the electronics (except the Qwiic OLED display) are mounted on a single circuit board. ESP32 WiFi / Bluetooth antenna, GNSS antenna, and timing pulse output are all connected via robust SMA connectors. IO connections are made via a robust 3.5mm header with cage screw connections. The timing pulse SMA output is 3.3V by default but can be configured for 5V if needed and is good for 100kHz (but not in NTP mode, that's fixed at 1Hz). The Reset and Mode switches have been positioned carefully; Mode is easily clicked when required, and Reset is flush and requires a more assertive press. (This helps prevent any accidental resets when connecting to the ESP32 USB port.) The edge of the microSD card protrudes slightly when inserted, making it easy to eject and re-insert. Then there is the beautiful custom extruded aluminum case with machined end panels and slotted flanges, making it simple to install the Reference Station in a weatherproof enclosure up on the roof or in your server rack.

The Reference Station has multiple power options. It can be powered by any or all of the ESP32 USB connection; the u-blox ZED-F9P USB connection; a separate USB-C power port on the rear; Power-over-Ethernet (36V to 57V); a 5V pin on the IO screw header. The 5V IO pin can accept a maximum of 5.5V if required. The GNSS SMA antenna connection provides 5V for the included active L1/L2 antenna instead of the usual 3.3V. The Reference Station provides both short-circuit and open-circuit detection and protection for the antenna cable; symbols will flash on the OLED display if a short or open is detected.

This device can be used in multiple modes, including:

• GNSS Base Station with NTRIP - RTCM corrections are sent to a Caster over Ethernet
• Network Time Protocol (NTP) Server - providing high-accuracy timing data to other machines via an Ethernet network

Those two modes are the ones most users will want to use, but you never cease to amaze us with the variety of ways you use our products. Should you want to, the Reference Station can also be used as:

• GNSS Positioning Receiver (~30cm accuracy) - also known as 'Rover'
• GNSS Positioning with RTK (1.4cm accuracy) - also known as 'Rover with RTK Fix' - using NTRIP RTCM correction data over Ethernet or from your phone via Bluetooth
• GNSS NMEA/UBX TCP Client - sending NMEA and/or UBX navigation data to a remote server using TCP over Ethernet

Please see the Hookup Guide for more details on which configurations we've tried and tested.

Our kit includes everything you need to get up and running. Please see the 'Includes' tab for more information.

• Cased Reference Station
• L1/L2/L5 GNSS Surveying Antenna
• Reinforced RG58 TNC-SMA Cable (10m)
• SMA WiFi / Bluetooth Antenna
• 32GB microSD Card (Class 10)
• USB-C Power Supply (5V 1A wall charger)
• USB-C Cable (A to C, 2m)
• Ethernet Cable (CAT-6, 1m)

• ESP32-WROOM processor
  • Reverse Polarity (RP) SMA WiFi / BT antenna connection
• u-blox ZED-F9P multi-band GNSS module
  • Connected via SPI for high-speed data transfer
• microSD socket
  • Connected via 4-bit SDIO for high speed read and write
• WIZnet W5500 Ethernet interface
  • 10/100 Mbps with auto-negotiate
• ATECC608A Crypto Co-processor
  • Future upgrade; not currently supported by the RTK firmware
• OLED display
• SMA Time Pulse output
  • 3.3V default
  • Configurable for 5V
  • 100kHz maximum usable output
  • 1Hz output in NTP mode
• SMA GNSS antenna connection
  • 5V power for an active antenna
  • Short-circuit detection
  • Open-circuit detection
• Custom extruded aluminum case with machined end panels
  • IP42 ingress protection
  • A weatherproof enclosure is required for outdoor use
• Matte-effect front and rear stickers
• Power options:
  • ESP32 USB-C connector
  • u-blox GNSS USB-C connector
  • Rear USB-C power connector
  • Power-over-Ethernet (36V - 57V)
  • 5V I/O screw terminal (5.5V Maximum)

• RTK Product Manual
• Hookup Guide
• RTK Firmware Binaries
• RTK Firmware Uploader
• RTK Firmware Source
• u-blox GNSS Firmware Update GUI
• Hardware GitHub Repo
• Schematic
• Case Dimensions
• PCB Dimensions
• Arduino Examples / Test Sketches