RTK Reference Station

Description

The SparkFun RTK reference station is ideal for precise geolocation, measurement and time reference. It makes it extremely easy to set up a fixed-location NTRIP server, providing an RTK system and even to work as an NTP server.

RTK stands for Real Time Kinematics. An RTK-capable satellite positioning receiver acquires signals from global navigation satellite systems (GNSS) along with a correction data stream for better positioning accuracy. GNSS includes GPS (US), GLONASS (Russia), Beidou (China), Galileo (Europe) and special additional satellites (e.g. SBAS and QZSS). These signals alone provide a positioning accuracy of approximately 30 cm. The RTK receiver receives an additional RTCM (Real Time Correction Message) data stream and then calculates the location of the device to within 1 cm in real time. RTK works best when correction data is generated locally, and the accuracy of the receiver deteriorates as the distance (baseline) between it and the correction-generating 'base' increases. With just a few minutes of set-up, the SparkFun reference station allows correction data to be generated locally and made available via Ethernet.

The reference station is based on an ESP32-WROOM processor and a u-blox ZED-F9P multiband GNSS module. It runs on the same open-source software as SParkFun's other RTK products. The station has 10/100 Mbps Ethernet connectivity and can be powered by Power-over-Ethernet (PoE). The microSD card is connected via a 4-bit SDIO interface for high read and write speeds. The u-blox ZED-F9P GNSS module is connected via a high-speed SPI interface, which also provides a high GNSS data rate. An ATECC608A cryptographic coprocessor is also included on the board to allow you to write your own firmware and use the reference station to mine cryptocurrencies or space weather stations or to secure and authenticate GNSS data. The reference station can also act as an NTP server. Having its own NTP server allows computers on an Ethernet network to achieve much more accurate clock synchronisation. The station supports DHCP by default, but if there is a need to give it a permanent IP address - the DNS, gateway and subnet mask are also configurable.

The unit is designed to be robustly built and easy to use in laboratories. The electronics (with the exception of the Qwiic OLED display) are mounted on a single PCB. The WiFi and Bluetooth ESP32 antenna, GNSS antenna and timing pulse output are connected via robust SMA connectors. The IO connections are made using a robust 3.5mm connector with screw connections. The SMA timing pulse output is 3.3 V by default, but can be configured to 5 V if required and is suitable for 100 kHz (but not in NTP mode, which is configured for 1 Hz). The edge of the microSD card protrudes slightly when inserted, making it easy to eject and reinsert. There is also a custom extruded aluminium housing with machined end panels and slotted flanges, making it easy to install the reference station in a weatherproof enclosure on a roof or in a server rack.

The station has multiple power options. It can be powered by any or all ESP32 USB connections, u-blox ZED-F9P USB connection, separate USB-C power port on the rear, Power-over-Ethernet (36V to 57V), 5V pin on IO connector. GNSS SMA antenna connector provides 5V for the attached active L1/L2 antenna. The reference station provides short-circuit and open-circuit detection and antenna cable protection.

The unit can be used in a number of modes, including as:

• GNSS base station with NTRIP - RTCM corrections are sent to the Caster via Ethernet
• NTP (Network Time Protocol) server - providing highly accurate time data via Ethernet
• GNSS positioning receiver (accuracy up to 30 cm) - also known as "Rover".
• GNSS positioning with RTK (accuracy of 1.4 cm) - also known as "Rover with RTK correction" - using NTRIP RTCM correction data via Ethernet or from a phone via Bluetooth
• GNSS NMEA/UBX TCP client - sending NMEA and/or UBX navigation data to a remote server using TCP over Ethernet

This wide variety and multifunctionality makes the reference station widely applicable to GNSS positioning projects. Full documentation and examples of use are available on the product page.

Features

• 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)

Kit contains

• 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)