SparkFun RTK Express
The SparkFun RTK Express is an easy to use GNSS receiver for centimeter-level positioning.
Perfect for surveying, logging, and all types of post processing, this preprogrammed device can
also be used for autonomous driving, navigation, asset tracking and any other application where
there is a clear view of the sky. The RTK Express can also be used as a base station. With the
press of a button, two RTK Expresses can be used to create an RTK system capable of 14mm
horizontal positional accuracy. The built-in Bluetooth® connection via an ESP32 WROOM
enables the user to use the RTK Express with their choice of GIS application on a phone or
tablet. The built in battery allows for over five hours of field use and is compatible with common
USB battery banks.
We took all the lessons from the RTK Surveyor and built the RTK Express. The RTK Express is
built upon the same ZED-F9P u-blox receiver as the original RTK Surveyor so you can expect
the same incredible performance and rich feature set. The embedded display allows for
immediate feedback of horizontal positional accuracy, satellites in view, logging status, survey-in
status, battery level, Bluetooth® MAC, etc. The rocker switches found on the original have been
replaced by keypad buttons. We increased the battery to 1300mAh for a longer run time. The
internal switches have been replaced by a digital Mux allowing for some really exciting
applications including event triangulation. More ESD protection was added to protect the RF
path, and we even threw in an accelerometer for digital leveling in the field.
The RTK Express works with common GIS software including SW Maps, SurvPC, Field Genius,
and any GIS software that supports NMEA over Bluetooth.
This device can be used in four modes:
•
•
•
•
GNSS Positioning (~30cm accuracy)
GNSS Positioning with RTK (1.4cm accuracy)
GNSS Base Station
GNSS Base Station NTRIP Server
In Position mode the device receives L1/L2 signals from a user-provided antenna and the highgrade GNSS receiver provides lat/long and altitude with accuracies around 300mm.
In Positioning with RTK mode the device receives L1/L2 signals from the antenna and
correction data from a base station. The correction data can be obtained from a cellular link to
online correction sources or over a radio link to a second RTK Surveyor/Express setup as a base
station.
In Base Station mode the device is mounted to a temporary position (like a tripod) and begins
transmitting correction data over a radio or Internet connection. A base is often used in
conjunction with a second unit set to 'Positioning with RTK' to obtain the 14mm relative accuracy.
The RTK Surveyor and RTK Express are interchangeable as a Base Station; an RTK Surveyor
can be a base for an RTK Express and vice versa.
In Base Station NTRIP Server mode the device is mounted to a semi or permanently fixed
position (like a roof) and connects over WiFi to transmit the correction data to a NTRIP caster so
that any rover can access the correction data over a cellular or Internet connection. This type of
base is a very easy way to set up a very precise absolute correction source.
Two cables are provided with the RTK Express allowing a user to plug in our easy to use Serial
Telemetry Radios or their own radio link. If a local correction source is within 10km, a user can
also use their phone to provide correction data over the Bluetooth® link (no external radio
needed!).
Note: The SparkFun RTK Express is just the enclosed device and does NOT include an
antenna, serial telemetry radio, or associated mounting pieces. These items will need to be
purchased separately from the Hookup Accessories below.
GNSS Receiver: ZED-F9P
•
•
•
•
•
•
•
•
Concurrent reception of GPS, GLONASS, Galileo and BeiDou
Receives both L1C/A and L2C bands
Current: 68mA - 130mA (varies with constellations and tracking state)
Time to First Fix: 25s (cold), 2s (hot)
Max Navigation Rate:
o PVT (basic location over UBX binary protocol) - 25Hz
o RTK - 20Hz
o Raw - 25Hz
Horizontal Position Accuracy:
o 2.5m without RTK
o 0.010m with RTK
Max Altitude: 50km (31 miles)
Max Velocity: 500m/s (1118mph)
Bluetooth® Transceiver: ESP32 WROOM
•
Xtensa® dual-core 32-bit LX6 microprocessor
•
•
•
•
•
•
•
Up to 240MHz clock frequency
4MB of flash storage
520kB internal SRAM
Integrated 802.11 BGN WiFi transceiver
Integrated dual-mode Bluetooth® (classic and BLE)
Hardware accelerated encryption (AES, SHA2, ECC, RSA-4096)
2.5 µA deep sleep current
Overall Device
•
•
•
•
•
•
•
•
•
Internal Battery: LiPo 1300mAh with 500mA charging
Radio Port: 3.3V TTL Serial (57600bps RTCM TX/RX)
Data Port: 3.3V TTL Serial (115200bps NMEA)
Embedded OLED Display for available satellites, data logging, and more.
Push button controls
Weight: 162g (entire device including battery)
Dimensions: 132mm x 101mm x 32mm (5.2in x 3.9in x 1.2in)
1x Qwiic Connector
Works with common GIS software including: SW Maps, SurvPC, Field Genius, et al.
0
