SparkFun RTK Facet L-Band

Designed and manufactured in Boulder, Colorado, USA, the SparkFun RTK Facet L-Band is your one-stop shop for high precision geolocation and surveying needs. For basic users, it’s incredibly easy to get up and running; for advanced users, the RTK Facet L-Band is a flexible and powerful tool. With just the press of a button, the RTK Facet L-Band is the fastest way to take centimeter-grade measurements. With built-in corrections, 14mm Real Time Kinematic fixes are less than a minute away. By connecting your phone to the RTK Facet L-Band over Bluetooth®, your phone or tablet can receive the NMEA output and work most GIS software. This is exactly how $10,000 surveying devices have been operating for the past decade - we just made it faster, more precise, and a lot more economical.

The RTK Facet L-Band works with common GIS software for Android and iOS including SW Maps [Android](https://sparkfun.github.io/SparkFun_RTK_Firmware/gis_software/#sw-maps) / [iOS](https://apps.apple.com/us/app/sw-maps/id6444248083), [Field Genius](https://www.microsurvey.com/products/fieldgenius-for-android/), [SurvPC](https://www.carlsonsw.com/product/carlson-survce), [Survey Master](https://docs.sparkfun.com/SparkFun_RTK_Firmware/gis_software/#survey-master), [Vespucci](https://play.google.com/store/apps/details?id=de.blau.android&hl=en_US&gl=US), [QGIS](https://qgis.org/), [QField](https://docs.qfield.org/get-started/), and any GIS software that supports NMEA over Bluetooth.

The RTK Facet L-Band utilizes corrections from u-blox\'s PointPerfect service broadcast from a geosynchronous Inmarsat satellite. The only setup required is a WiFi SSID and password. Once entered, the device will provision itself and periodically (once a month) update the decryption keys necessary to use the PointPerfect service. The price of the RTK Facet L-Band includes a 12-month subscription. Additional years of service can be purchased.

Under the hood of the SparkFun RTK Facet L-Band is an ESP32 WROOM connected to a ZED-F9P GNSS receiver, a NEO-D9S L-Band receiver (for corrections), and a variety of peripheral hardware (LiPo fuel gauge, microSD, etc). Additionally, housed under the dome of the RTK Facet L-Band is a surveyor grade L1/L2/L-Band antenna. This antenna is a unique combination of elements designed to receive the GNSS signals (L1/L2) alongside the 1.55GHz PointPerfect corrections. The built-in antenna has an ARP of 69mm from the base to the measuring point of the L1 antenna and an ARP of 68mm to the measuring point of the L2 antenna. The RTK Facet L-Band is programmed in Arduino and can be tailored by you to fit whatever your needs may be.

This device can be used in five modes:

* GNSS Positioning (~30cm accuracy) - also known as \'Rover\'
* GNSS Positioning with RTK L-Band (1.4 to 6cm accuracy) - also known as \'Rover with L-Band RTK Fix\'
* GNSS Positioning with RTK (1.4cm accuracy) - also known as \'Rover with RTK Fix\'
* GNSS Base Station
* GNSS Base Station NTRIP Server

At *Power On* the device will enter Rover or Base mode; whichever state the device was in at the last power down. When the POWER/SETUP button is pressed momentarily, a menu is presented to change the RTK Facet L-Band to Rover or Base mode. The display will indicate the change with a small car or flag icon.

In *Rover mode* the RTK Facet L-Band will check if WiFi is available and update any L-Band keys needed (keys expire every 56 days). The device will automatically begin receiving and decrypting position correction data. Simultaneously, the RTK L-Band will receive L1 and L2 GNSS signals from the four constellations (GPS, GLONASS, Galileo, and BeiDou). The device will calculate the position based on the combination of GNSS and correction signals. The receiver will quickly (within 60 seconds) obtain an RTK float, then fix. Similar to a standard grade GPS receiver, the RTK Facet L-Band will output industry standard NMEA sentences at 4Hz and broadcast them over any paired Bluetooth® device. The end user will need to parse the NMEA sentences using commonly available mobile apps, GIS products, or embedded devices (there are many open source libraries). Unlike standard grade GPS receivers that have 2500mm accuracy, the accuracy in this mode is approximately 14 to 60mm horizontal positional accuracy.

If the device is in *Rover mode* but L-Band is not available, regular RTCM based RTK is still available. When RTCM correction data is sent over Bluetooth® or into the radio port, the device will automatically enter Positioning with RTK mode. In this mode RTK Facet L-Band will receive L1/L2 signals from the antenna and correction data from a base station. The receiver will quickly (within a second) obtain an RTK float, then fix. The NMEA sentences will have increased accuracy of 14mm horizontal and 10mm vertical accuracy. The RTCM correction data is most easily obtained over the Internet using a free app on your phone (see SW Maps or Lefebure NTRIP) and sent over Bluetooth® to the RTK Facet L-Band but RTCM can also be delivered over an external cellular or radio link to a 2nd RTK Facet, Surveyor, Express, etc setup as a base station.

In *Rover mode* the RTK Facet L-Band will receive L1 and L2 GNSS signals from the four constellations (GPS, GLONASS, Galileo, and BeiDou) and calculate the position based on these signals. Similar to a standard grade GPS receiver, the RTK Facet L-Band will output industry standard NMEA sentences at 4Hz and broadcast them over any paired Bluetooth® device. The end user will need to parse the NMEA sentences using commonly available mobile apps, GIS products, or embedded devices (there are many open source libraries). Unlike standard grade GPS receivers that have 2500mm accuracy, the accuracy in this mode is approximately 300mm horizontal positional accuracy.

In *Base mode* the device will enter Base Station mode. This is used when the device is mounted to a fixed position (like a tripod or roof). The RTK Facet L-Band will initiate a survey. After 60 to 120 seconds the survey will complete and the RTK Facet L-Band will begin transmitting RTCM correction data out the radio port. A base is often used in conjunction with a second RTK Facet L-Band (or RTK Surveyor, Express, Express Plus, etc) unit set to \'Rover\' to obtain the 14mm accuracy. Said differently, the Base sits still and sends correction data to the Rover so that the Rover can output a really accurate position.

In addition to supplying position data the RTK Facet L-Band is capable of logging NMEA, RAWX, and SFRBX for post processing making it ideal for research and advanced positioning applications.

The RTK Facet L-Band is an open source hardware product meaning you can fully obtain, see, and even modify the electrical and mechanical design files. This allows for easier maintenance and repair over time.

The SparkFun RTK Facet L-Band kit includes everything you need: the enclosed device, correction subscription for 12 months, thread adapter, charger, data cables, and carrying case. It does NOT include a surveying pole. These items will need to be purchased separately.

Please Note: PointPerfect L-Band correction service for the SparkFun Facet L-Band is currently only available in the USA\'s 48 contiguous states and the European Union shown in the coverage map below. More information on PointPerfect can be found here.

Important: The SparkFun RTK Facet L-Band is not designed for permanent outdoor mounting. Please use the L1/L2 antenna (which we\'ve had outside constantly for over three years in Colorado UV) mounted outside with a cable running to the RTK Surveyor that is located inside or protected from the elements. Or, for a cheaper solution, the ESP32 attached to our ZED-F9P breakout is a great way to go. See our How to Build a DIY GNSS Reference Station tutorial for more information.

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