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 The rocker switches found on the original have been replaced by keypad buttons.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 The internal switches have been replaced by a digital Mux allowing for some really exciting applications including event triangulation.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.
This device can be used in four modes:
In Position mode the device receives L1/L2 signals from a user-provided antenna and the high-grade 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!).
We are undergoing FCC/CE EMI and safety testing for the RTK Express. Once complete the RTK Express will become a mainstream SparkFun product. For now, this is fully capable, fully programmed, but consider it a device in development.
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
Bluetooth® Transceiver: ESP32 WROOM
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Skill Level: Competent - The toolchain for programming is a bit more complex and will examples may not be explicitly provided for you. You will be required to have a fundamental knowledge of programming and be required to provide your own code. You may need to modify existing libraries or code to work with your specific hardware. Sensor and hardware interfaces will be SPI or I2C.
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If it requires power, you need to know how much, what all the pins do, and how to hook it up. You may need to reference datasheets, schematics, and know the ins and outs of electronics.
Skill Level: Rookie - You may be required to know a bit more about the component, such as orientation, or how to hook it up, in addition to power requirements. You will need to understand polarized components.
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Initial out of box was easy. Am still attempting to link with my FTM400. The 900 MHz units shown in the set up Youtube are no longer available so I'm going with the higher power licensed unit and avoid extra stations. To do this as required I still need a laptop sized program that will convert the output to cadestral