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SparkFun RTK Facet

Designed and manufactured in Boulder, Colorado, USA, the SparkFun RTK Facet is your one stop shop for high precision geolocation and surveying needs. For basic users, it’s incredibly easy to get up and running and for advanced users, the RTK Facet is a flexible and powerful tool. With just a few minutes of setup, the RTK Facet is one of the fastest ways to take centimeter grade measurements. By connecting your phone to the RTK Facet over Bluetooth®, your phone can act as the radio link to provide correction data as well as receive the NMEA output from the device. This is exactly how $10,000 surveying devices have been operating for the past decade - we just made it easier, smaller, and a lot more economical.

Under the hood of the SparkFun RTK Facet is an ESP32 WROOM connected to a ZED-F9P as well as some peripheral hardware (LiPo fuel gauge, microSD, etc). Additionally, housed under the dome of the RTK Facet is a surveyor grade L1/L2 antenna. It is the same element found within our GNSS Multi-Band L1/L2 Surveying Antenna. The built in antenna has an ARP of 61.4mm from the base to the measuring point of the L1 antenna and an ARP of 57.4mm to the measuring point of the L2 antenna. The RTK Facet is programmed in Arduino and can be tailored by you to fit whatever your needs may be.

This device can be used in four modes:

  • GNSS Positioning (~30cm accuracy) - also known as 'Rover'
  • 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 to Rover or Base mode. The display will indicate the change with a small car or flag icon.

In Rover mode the RTK Facet 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 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 with a good grade L1/L2 antenna.

When the device is in Rover mode and 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 will receive L1/L2 signals from the antenna and correction data from a base station. The receiver will quickly (within a second) obtain 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 but RTCM can also be delivered over an external cellular or radio link to a 2nd RTK Facet setup as a base station.

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 will initiate a survey. After 60 to 120 seconds the survey will complete and the RTK Facet will begin transmitting RTCM correction data out the radio port. A base is often used in conjunction with a second RTK Facet (or RTK Surveyor) 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. You’ll create an RTK system without any other setup.

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

The RTK Facet 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.

Note: The SparkFun RTK Facet is just the enclosed device with thread adapter, charger, and data cables. It does NOT include serial telemetry radio or associated mounting poles. These items will need to be purchased separately.

Note: The SparkFun RTK Facet is not designed for permanent outdoor mounting. Please use the L1/L2 antenna (which we've had outside constantly for nearly 2 years in Colorado UV) with a cable running to the RTK Surveyor, 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.

Overall Device

  • Enclosed Facet Design IP53 - Protected from limited dust ingress and water spray
  • Internal Antenna: L1/L2 with ≥5dBi gain
  • Internal Battery: LiPo 6Ah with fast 1 amp charging
  • Radio Port: 3.3V TTL Serial (57600bps RTCM TX/RX)
  • Data Port: 3.3V TTL Serial (115200bps NMEA)
  • Qwiic Port: Supports I2C based add-on devices
  • microSD: Compatible up to 32GB
  • Embedded OLED Display for positional accuracy, available satellites, data logging, etc.
  • Single push button control
  • Weight: 583g (1.3 lbs)
  • Dimensions: 136mm x 146mm x 80mm (5.35in x 5.74in x 3.14in)
  • Open Source Hardware Certified Project
  • Manufactured in Boulder, CO USA

GNSS Receiver: ZED-F9P

  • Concurrent reception of GPS, GLONASS, Galileo and BeiDou
  • Receives both L1C/A and L2C bands
  • 184-channel u-blox F9 engine
  • Current: 68mA - 130mA (varies with constellations and tracking state)
  • Time to First Fix: 25s (cold), 2s (hot)
  • Max Navigation Rate:
    • PVT (basic location over UBX binary protocol) - 25Hz
    • RTK - 20Hz
    • Raw - 25Hz
  • Horizontal Position Accuracy:
    • 2.5m without RTK
    • 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

SparkFun RTK Facet Product Help and Resources

How to Build a DIY GNSS Reference Station

October 15, 2020

Learn how to affix a GNSS antenna, use PPP to get its ECEF coordinates and then broadcast your own RTCM data over the internet and cellular using NTRIP to increase rover reception to 10km!

Setting up a Rover Base RTK System

October 14, 2020

Getting GNSS RTCM correction data from a base to a rover is easy with a serial telemetry radio! We'll show you how to get your high precision RTK GNSS system setup and running.

SparkFun RTK Facet L-Band Hookup Guide

June 9, 2022

Setup the RTK Facet L-Band in minutes to begin gathering millimeter level geospatial coordinates.

How to Upgrade Firmware of a u-blox GNSS Receiver

March 26, 2021

A few steps and you'll upgrade to the latest features on a u-blox GNSS receiver.

SparkFun RTK Facet Hookup Guide

December 16, 2021

Setup the RTK Facet in minutes to begin gathering millimeter level geospatial coordinates.

Core Skill: DIY

Whether it's for assembling a kit, hacking an enclosure, or creating your own parts; the DIY skill is all about knowing how to use tools and the techniques associated with them.


Skill Level: Noob - Basic assembly is required. You may need to provide your own basic tools like a screwdriver, hammer or scissors. Power tools or custom parts are not required. Instructions will be included and easy to follow. Sewing may be required, but only with included patterns.
See all skill levels

Core Skill: Programming

If a board needs code or communicates somehow, you're going to need to know how to program or interface with it. The programming skill is all about communication and code.

3 Programming

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.
See all skill levels

Core Skill: Electrical Prototyping

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.

2 Electrical Prototyping

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.
See all skill levels


Looking for answers to technical questions?

We welcome your comments and suggestions below. However, if you are looking for solutions to technical questions please see our Technical Assistance page.

  • Soledad / about 2 years ago / 1

    Do you plan Septentrio Mosaic-X5 receiver module for your facet unit? It is three frequency.

    • We've looked into the Septentrio and will continue to watch the capabilities of the Mosaic but we don't have any plans to create a Mosaic based version right now.

  • Member #517719 / about 2 years ago / 1

    Any recommendations or clues on what mounting poles to buy and the best place to source them?

    • Yup! Checkout the hookup guide, specifically Hardware Assembly. tldr; Monopods or Tripods with 1/4" screws work well for light field work.

      • Member #517719 / about 2 years ago / 1

        Thanks Nate! As my finger was heading to submit the reply I was thinking to myself - I probably should check out the hookup guide.

  • Member #1483736 / about 2 years ago / 1

    Typos, gps accuracy 2500mm not 2500m

  • Yashu / about 2 years ago / 0

    Can you advise when the LTE / WiFi / 915MHz radio PCBs will be available? Can the radio board upgrades be performed in the field by the astute customer?

Customer Reviews

3.5 out of 5

Based on 15 ratings:

Currently viewing all customer reviews.

1 of 1 found this helpful:

The best of the best!

The SparkFun RTK Facet far exceeded my expectations. It arrived with the battery support broken since the battery internally moves, but easy to uncover and adjust the battery in a better way, in a new version maybe this can be improved.

Hello & thank you for the review. As noted in a previous comment response, we have worked to replicate the issue with the battery support that you described through what we call "very destructive testing;" dropping the unit, on its side, 1m above the ground, directly onto a face, onto concrete. We are surprised the unit failed in shipping given how much is required to replicate in testing, but (in our testing) the unit continued to operate once removing the broken plastic piece; we are glad your unit is still working as well! We suspect that other customers may face this issue under normal to rough usage, so, we have a stop-gap in place (as of Jan 21, 2022) of applying VHB (very high bond) tape between the battery and enclosure. Replicating the drop tests previously mentioned, this VHB has shown to significantly increase durability. Additionally, we are working on a more permanent long-term solution. If you have not already reached out to our support department please do and we will help you implement this stop-gap on your unit. Cheers!

3 of 3 found this helpful:

So far, so good

Works fine, tested to less than 2cm error over bench marks using the MNDOT VRS network as a correction source. Trying PPP this weekend.

Gave a 4 out of 5 because the battery was loose inside the housing. Heard a rattle, opened it up, and the foam placed between the battery and antenna was too thin, so the battery could rattle around and perhaps detach. I cut some flexible dense foam to fit, put the unit back together, and seems to work fine. Not sure how well the black gasket cover seals against water, I sealed the upper lip with somie silicon grease. Probably not as robust as my Trimble or Arrow units, but if I’m not too rough on it I should be alright, and it has equal accuracy for 1/10th the cost.

1 of 1 found this helpful:

So far, so good.

I'm giving the RTK Facet 4 stars only because it has not been tested enough to give five. More time is required to see if data is reproducible.

1 of 2 found this helpful:

Arrived broken

I was excited to try this fantastic sounding product but was disappointed when I picked up the box and it rattled. The battery pack was loose, a plastic piece holding the battery in place broke during shipping. I believe this happened because it was either improperly packed for shipping or needs improved mounting tabs to restrain the battery pack. I returned this item and am hesitant to order another one if they are that delicate.

Hello & thank you for the review. We have worked to replicate the issue that you described through what we call "very destructive testing;" dropping the unit, on its side, 1m above the ground, directly onto a face, onto concrete. We are surprised the unit failed in shipping given how much it required to replicate in testing, but (in our testing) the unit continued to operate once removing the broken plastic piece. We suspect that other customers may face this issue under normal to rough usage, so, we have a stop-gap in place (as of Jan 21, 2022) of applying VHB (very high bond) tape between the battery and enclosure. Replicating the drop tests previously mentioned, this VHB has shown to significantly increase durability. Additionally, we are working on a more permanent long-term solution. We hope this will give you the confidence to try SparkFun RTK products again soon. Cheers!

0 of 1 found this helpful:

Great potential. Not very sturdy.

Won't comment on all the great features as this can be read on the guides. The Ublox chip's performance is well known to be great. I will say that the unit is not very strong and needs to be handled with more care than traditional devices. Also water damage is more likely if not carefull. My unit arrived with a broken plastic piece which rattled inside. This was part of the battery support and required a small fix.

0 of 1 found this helpful:

Damaged product

I'm from Ecuador, I brought the product with the greatest possible care, paying even extras, but the product arrived loose the battery with broken pieces inside, it turned on once and then we checked nothing with my team and inside the plate is as if it had been removed from an old equipment, damaged cables, circuits that were not worth the truth, I do not recommend it to those who read this, it could be a loss. DO NOT BUY IT

0 of 1 found this helpful:

Comes broken. Hard to firmware update.

It came with a broken battery holder, although it was easy to repair. I had a lot of trouble updating the firmware (Achieved thanks to the support of Nathan Seidle) . Now the Power/setup button doesn't work. I was only able to use it once in the field. I think the product is a good idea that needs to be improved, now I am waiting for instructions for its replacement.

Update: The button issue was my fault, as I left the button ribbon bent and pressed making poor contact when I reassembled the unit after removing the sd card from inside the unit.

Now it's working great.

I leave 4 stars because of the fragility of the battery holder.

0 of 1 found this helpful:

Does not work with IOS

I have not been able to use it yet because there is no App for IOS even though it says it supports IOS. It looks like I will need to at least purchase an Android phone just to test it it out.

Didn't work

Couldn't connect via bluetooth, eventually the unit became totally inoperative. SparkFun have now returned the item to them for repairs, thank you for that. Potentially a very impressive unit, looking forward to its return and possibly a second unit to act as correction data base as we have no phone/internet. Disappointed but not put off.

Fantastic capabilities, but brittle design…

When I received my RTK Facet it was not working. I posted on the forum about my journey to make it work. Most likely, there was a bad connection on the OLED. I disassembled it, debugged it, reassembled it (with help of Sparkfun support) and I now have an up and running RTK Facet. It would definitively worth a five star review (*****) if it would have work out of the box.

Few more comments…

I’m definitely not into over packaging, but RTK Facet was shipped in a box with only some paper to prevent from shocks for international shipping.

I would like to be able to buy RTK Facet parts separately in case of an eventual failure. Sparkfun kindly offer me fixing it, but international shipping round trip is not an easy option.

Overall a beautiful piece of technology!

Great RTK!

I bought this Rtk and it is working so well! I haven't had any issues until now. We are using this rtk as base in a drones swarm. Our drones are using M8P module and it is working well.

Worked great right out of the box

After reading the reviews I was expecting the worst. But thankfully I was completely happy with the unit when it arrived. No issues with the shipping, it powered right up and worked perfectly. Already have it connected to our Carlson data collector and plan to field test it by surveying a few lots in the next few days. It does seem a bit delicate, but I think that might be due to how little it weighs. I can already tell we will be buying a few more of these.

good value for money

First, it works. Given the price, that's pretty great. My unit did not have the issues with the battery that were described in other reviews. Build quality seems appropriate for the price.

The antenna can see more satellites than i'd have expected from under tree canopy.

I've seen > 1 meter differences from day to day in "RTK Fix" positions of the same point, that the Facet reported as less-than-20mm accuracy. This could be due to erroneous data from the NTRIP server (I'm using a public one only a few km away but one can't rely on them for anything real). But still, > 1 meter is a lot of variation.

The 900 MHz Holybro telemetry radios (v3) are indeed "plug and play." But they're also pretty low power and have small antennas, so not a lot of range is available. I wasn't able to get higher-power 900 MHz telemetry radios to work.

All in all, you can do useful things with the Facet, but the products surrounding it are not robust enough for the fixes to be trusted without additional post-processing.



Phenomenal GNSS Receiver

This is a phenomenal GNSS receiver, at any price, but especially at this price. I am an archaeologist who has been using Emlid receivers for a few years now. I ordered two Facet's to replace my existing setup. I've tested my Facets in the field using our local base station network, and will be using them in the coming months in a base/rover setup. My initial experience shows the Facet outperforming my earlier setup in time to setup, ease-of-use, and accuracy. The open source nature of this is great as well, and seamlessly integrates with my QGIS field mapping workflow already in place. I couldn't be happier!