Setup guide for u-blox's automotive GNSS evaluation kit (EVK-M8L/M8U)

"We want to know the exact location of vehicles even in tunnels and under elevated tracks."
For ECU development engineers facing such challenges.
This article provides a clear explanation of the setup procedure using u-blox's automotive GNSS evaluation kit "EVK-M8L/M8U" and how to use it in actual driving tests.

Reliable even in places where GNSS cannot reach! The innovative technology of dead reckoning x IMU

"In developing autonomous driving in urban areas, misalignment in tunnels has been a major issue."
An ECU development manufacturer was struggling with positioning accuracy in environments where GNSS signals were blocked. They implemented the u-blox EVK-M8U evaluation kit. By utilizing the IMU and Dead Reckoning, they were able to obtain stable positioning information even inside tunnels, and the development team praised the kit, saying, "The accuracy of driving logs has improved dramatically." Furthermore, the automatic calibration function of the IMU sensor, which aims to improve the accuracy of the dead reckoning function, allowed them to move on to the actual driving test phase just one week after installation in the vehicle.

Before introducing the latest GNSS positioning technology, let's take a brief look at the historical dead reckoning technology.
Dead reckoning developed in ancient navigators as a technique for estimating current position based on the direction of travel and distance traveled from a starting point. On ships, direction was confirmed using a compass, and distance was calculated by measuring speed and time using a log (current meter) or hourglass, and this was recorded on a nautical chart to estimate position.
However, this method led to accumulated errors, so astronomical observations using a sextant were also used to correct the latitude and maintain the accuracy of the route.
These technologies played a role equivalent to today's GNSS technology in exploration and trade during the Age of Discovery.

A historical overview of dead reckoning technology

With the development of modern technology, classical dead reckoning technology has evolved into GNSS positioning technology, which uses signals from positioning satellites and ground stations to estimate position. Furthermore, by automating positioning and calibration, it is now possible to calculate absolute position in real time with an accuracy of centimeters to several meters.
This technology is the foundation of current automobile navigation systems.

What is the EVK-M8L/M8U? Basics and differences of the in-vehicle GNSS evaluation kit

Appearance of EVK-M8L (left) and EVK-M8U (right)

The EVK-M8L/M8U are high-precision GNSS evaluation kits for automotive use provided by u-blox. The M8L is equipped with dead reckoning functionality, while the M8U integrates an IMU, enabling both to provide highly accurate positioning information. IMU stands for Inertial Measurement Unit and refers to a unit that combines an accelerometer and gyroscope. It detects vehicle movement (acceleration and angular velocity) with high precision, and by using IMU data, it can continue to estimate position even in environments where GNSS signals are blocked. This sensor information is then combined using a Kalman FILTERS to achieve highly accurate navigation.

The EVK-M8L/M8U has the following three features that make it highly practical for in-vehicle GNSS evaluation:

Feature 1: Not just GNSS! Dead Reckoning for accurate positioning even in tunnels
Feature 2: No external sensors required! Easy on-board high-precision evaluation
Feature 3: Complete with just one USB! From setup to log acquisition

Below we will explain in detail the features of the EVK-M8L/M8U.

[Feature 1] Not just GNSS! Dead Reckoning for accurate positioning even in tunnels

When using GNSS alone for positioning, satellite signals can be interrupted in environments with many obstructions, such as high-rise buildings or tunnels, making positioning unstable or impossible.Dead Reckoning is a technology that enables highly accurate positioning even in such environments by integrating information from gyro sensors and accelerometers and performing calculations.

u-blox's Dead Reckoning

u-blox's Dead Reckoning-compatible products combine absolute speed and distance from the vehicle wheels with relative information from acceleration and gyro sensors to achieve continuous positioning even in situations where GNSS signals cannot be received.
The EVK-M8L supports ADR (Automotive Dead Reckoning), which utilizes external signals from the vehicle, while the EVK-M8U supports UDR (Untethered Dead Reckoning), which operates without external signals. This enables highly accurate positioning even in environments where GNSS signals are blocked, such as tunnels and urban areas.

[Feature 2] No external sensors required! Easy on-board high-precision evaluation

The EVK-M8L/M8U is equipped with the NEO-M8L/M8U module. The NEO-M8L/M8U module has built-in accelerometers and gyro sensors, allowing standalone evaluation without the need for external sensors. Furthermore, the design concept allows for the flexible use of data from multiple types of sensors installed in the vehicle, depending on the application and accuracy requirements, and on the cost and performance of the navigation system.

<Key features and technical advantages of u-blox Automated Dead Reckoning>

• Highly accurate position estimation is possible by directly acquiring and utilizing data from other sensors installed in the vehicle via the vehicle's communication bus.
• It can be flexibly adapted to suit various applications, from a high-precision configuration that combines a wheel stick, gyro, and acceleration sensor, to a simple configuration that uses only a wheel stick.
• It is designed to minimize the host processing load required to run Dead Reckoning.
• The software calibration function automatically corrects installation errors of the sensor head unit.
• It supports a variety of sensor configurations and can flexibly adapt to various vehicle models.
• It has a wide range of communication interfaces including I2C, SPI, UART, and USB.
• Initial and ongoing self-calibration automatically compensates for the effects of sensor aging and temperature changes.
• Stable operation is possible even in low wheel tick environments.
• It is equipped with an external FLASH MEMORIES, and with future improvements and updates, it will be compatible with new GNSS systems such as Galileo.
• It has a built-in map matching input function, which allows for further improvement of navigation performance.

u-blox M8 Automated Dead Reckoning Implementation Example

Here we will introduce an example of implementing automatic dead reckoning functionality in the u-blox M8 series.
This implementation fuses GNSS signals with vehicle sensor data to enable highly accurate position estimation even in environments where satellite signals are disrupted.

Sensor configuration (left side)
The following vehicle sensor data is used:

• Accelerometer: Detects acceleration in the x, y, and z axes
• Angular ANGULAR VELOCITY SENSORS Rate: Detects yaw angle (vehicle turning)
• Wheel Ticks (vehicle speed pulse): Detects vehicle speed
• Direction: Obtains directional information such as forward and backward movement.
These sensor data are sent to a central processing system and integrated with GNSS.

GNSS integrated processing (right side)
The blue box on the right, "RF Front-End & GNSS Channels", does the following:

• Correlators, Range Calculation: GNSS signal correlation processing and distance calculation
• Position Calculation + Dead Reckoning: Position estimation and dead reckoning using GNSS and sensor data
• Kalman Filter Blending: Data fusion using Kalman FILTERS
• Weighting Inputs Depending on Quality: Weighting process according to the quality of sensor data
This integration process ultimately outputs "Position, Velocity, Time."

Dead Reckoning accuracy in parking lots. Maintains accurate position even when GNSS signals are interrupted.

The image above shows the results of a parking lot drive test using u-blox's automatic dead reckoning function. The vehicle's position was accurately tracked throughout the five-story parking lot, including multiple 360-degree turns. Despite the GNSS satellites being out of view during the drive test, the vehicle was correctly positioned in the center of the left lane upon exiting the parking lot, proving the effectiveness of the automatic dead reckoning function.

The self-calibration feature minimizes the need for manual sensor mounting positioning, vehicle signal polarity and logic level adjustment, and host application integration, reducing risk, cost, and speeding time to market. This makes the sensor compatible with virtually all vehicle models and drivetrains (front-wheel drive, rear-wheel drive, all-wheel drive, etc.). It's also suitable for many car telematics applications, including car navigation, eCall, mileage-based insurance, road tolls, and stolen vehicle tracking.

[Feature 3] All you need is a single USB cable! Everything from setup to log acquisition

The EVK-M8L/M8U can be POWER SUPPLIES and communicates via a USB port, making it easy to set up a measurement environment. Using the u-blox GUIs u-center and u-center 2, you can efficiently configure the GNSS module, visualize data, and acquire logs on a PC.

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  u-center

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  u-center 2

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  u-blox evaluation software comparison table

■ u-center (conventional)
This is evaluation software for conventional GNSS products such as u-blox M8/M9/F9. It has a flexible UI and powerful logging functions, allowing you to check the operation of GNSS services and change their settings. It is an industry-standard tool that is also widely used for RTK positioning.

■ u-center 2 (new generation)
This is evaluation software for the latest GNSS products such as u-blox M10/F10/X20. It features an intuitive UI, a personalizable workspace, log playback function, automatic updates, and more, making evaluation and configuration tasks more efficient.

The next chapter explains the process from setting up the evaluation kit to verifying its operation.

Try it on the actual machine! Steps from setup to driving test

The setup of the EVK-M8L/M8U consists of clear steps, such as connecting the hardware, installing the software, and verifying initial communication. For the M8U in particular, IMU sensor calibration is key to improving accuracy.

Test vehicle preparation and signal acquisition points

For the EVK's dead reckoning function to operate accurately, it is essential to obtain the WHEELTICK signal (vehicle speed pulse) and FWD signal (heading direction) from the vehicle. If you have Access to the vehicle's CAN messages, you can input this information as UBX-ESF-MEAS messages to the EVK-M8L's communication port (e.g., software interface). In the EVK-M8L's default configuration, the WHEELTICK and FWD signals are set as input from the hardware. If you want to obtain this information using UBX-ESF-MEAS messages, you must change the configuration using the UBX-CFG-ESFWT command. (For details about the software interface, refer to the separate protocol specification.)

Vehicle speed pulse WHEELTICK signal and forward direction FWD signal input configuration diagram

Hardware connection: Connect to PC, ANTENNAS, and OBD2

The EVK-M8L/M8U is connected to a PC using a USB CABLES or RS-232 CABLES. POWER SUPPLIES and communication are possible through the USB port, so no external POWER SUPPLIES is required. By connecting a GNSS ANTENNAS to the EVK, signals such as vehicle speed pulses and external IMUs can be input as needed. The EVK-M8U has a built-in IMU sensor, so no additional external sensors are required.
OBD2 devices are usually used for vehicle diagnosis, but in this configuration, vehicle speed information is acquired in digital format from the vehicle ECU via CAN communication in order to obtain driving logs. The acquired vehicle speed data is input into the EVK-M8L/M8U.

EVK-M8L/M8U connection configuration example (hardware input)

Software installation: How to use u-center

First, install the "u-center" software provided by u-blox on your PC. As explained earlier, u-center is an integrated tool that can configure GNSS modules, visualize data, acquire logs, and update firmware all in one place. It is compatible with Windows environments and is automatically recognized after USB connection, so it can be used immediately after installation.

Example of setting screen using u-center

After installing the software, launch u-center and check whether communication with the EVK-M8L/M8U has been established (see the u-center setting screen above, where a green icon within two red frames indicates that communication has been established). Information such as the GNSS signal reception status, number of captured satellites, and current position is visualized in real time, making it easy to check the communication status.

Calibration Settings: 5 Steps That Determine Accuracy

To perform a driving test with the EVK-M8L/M8U, you must first perform calibration settings. The following five settings are the main ones that are required.

1. How to automatically set the sensor mount alignment
2. Main unit and ANTENNAS installation position and lever arm settings
3. How to set and check the WHEELTICK and FWD signals
4. Saving and Reusing Settings: Procedure for Saving Configuration
5. Calibration run confirmation and status check

1. How to automatically set the sensor mount alignment

Automatic sensor mount alignment can be set using the "UBX-CFG-ESFALG" command in the "Message view" screen of u-center. Automatic IMU-mount Alignment is a function that automatically calibrates the mounting angle (Roll/Pitch/Yaw) of the IMU (Inertial Measurement Unit: accelerometer + gyroscope). If you want to automatically set the correct angle during the calibration run, check the "Automatic IMU-mount Alignment" box and then click the Send button.
*If the alignment angle of the sensor mount is known, enter the value directly in the UBX-CFG-ESFALG setting screen. At this time, uncheck "Automatic IMU-mount Alignment."

UBX-CFG-ESFALG setting screen

Auto Alignment can be checked in the UBX-ESF-ALG field. During sensor mount alignment calibration, the status of the UBX-ESF-ALG field will change as shown in the figure below. When calibration begins, the status display will be blank, but as calibration progresses, values will be displayed in Mounting-Roll/Pitch/Yaw, and if the Auto Alignment indicator finally changes to green "〇 (normal)", the calibration has completed successfully. *At this point, you need to confirm that the Auto Alignment indicator is green + "ON".

UBX-ESF-ALG field status transition

2. Main unit and ANTENNAS installation position and lever arm settings

• How to set up the EVK-M8L installation location

The installation positions of the EVK-M8L main unit and ANTENNAS are set using the "UBX-CFG-ESFLA" command in the "Message view" screen of u-center. Using the center of the rear wheel (VRP: Vehicle Reference Point) as a reference, enter the distances in the X, Y, and Z directions from the EVK-M8L (IMU) main unit to the installation position of ANTENNAS. Enter values only in the field on the left (red frame in the image below). Be careful not to enter values in the field on the right.

Evaluation kit (IMU) and ANTENNAS position diagram (EVK-M8L)

• How to set up the EVK-M8U installation location

For the EVK-M8U, use the UBX-CFG-ESFLA command in the same way to set the installation position of the main unit and ANTENNAS. The settings differ from those for the EVK-M8L mentioned earlier; you enter the distance in the X, Y, and Z directions to the VRP (center of the rear wheels) based on the installation position of the EVK-M8U (IMU) and ANTENNAS. Enter values only in the right-hand field. Be careful not to enter values in the left-hand field.
For the EVK-M8U, the evaluation kit must be fixed horizontally with the label facing up and the X direction facing the direction of travel. If the EVK is installed upside down or facing the opposite direction, the output of the gyro and accelerometer may have an incorrect sign (negative) when the vehicle is stopped.

EVK-M8U 3D coordinate system

Evaluation kit (IMU) and ANTENNAS position diagram (EVK-M8U)

3. How to set and check the WHEELTICK and FWD signals

When setting the WHEELTICK and FWD signals, you must properly set the FWD signal that determines whether the vehicle is moving forward or backward. To check the polarity of the FWD signal on an actual vehicle, you can measure the FWD signal level with a multimeter when the gear is set to forward. Use the UBX-CFG-ESFGAWT command on the Message view screen to properly set the Direction Pin Polarity (FWD) (see below). Normally, you do not need to change any parameters other than the polarity of the FWD signal. If you have changed the default values, click the Send button in u-center.

WHEELTICK and FWD signal setting screen

4. Saving and Reusing Settings: Procedure for Saving Configuration

The automatically acquired sensor mount alignment settings can be saved in the non-volatile memory of the EVK. The alignment information saved in the non-volatile memory is reloaded at cold start and is retained until the next automatic alignment is performed.
To save the sensor mount alignment settings to non-volatile memory:

① Open the UBX-CFG-ESFALG screen (see the bottom left), uncheck “Automatic IMU-mount Alignment”, and click the “Send” button.

②Next, by sending the UBX-CFG-CFG command on the UBX-CFG-CFG setting screen shown in the lower right figure, all ADR parameters, including alignment settings, can be saved to the BBR and non-volatile memory (Flash).

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  UBX-CFG-CFG setting screen

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  UBX-CFG-ESFALG setting screen

5. Calibration run confirmation and status check

The EVK uses the speed and heading information acquired from the vehicle or the information acquired by the built-in sensors (gyro and acceleration) to improve the accuracy of the dead reckoning (ADR) function. The EVK must collect enough driving data, including sufficient left and right turns, to complete the calibration of the sensor mount alignment. If the ADR settings are saved to FLASH MEMORIES, a calibration run is sufficient only once. The calibration status can be checked in the UBX-ESF-STATUS field. After checking the calibration status, a test drive is possible.

<Checking the calibration status>
It is best to perform the calibration run in an open area with a clear view of the sky, such as a large parking lot with no parked vehicles.

① You can check the progress of the calibration with the following two types of UBX messages:
UBX-ESF-STATUS: Overall calibration status
UBX-ESF-MEAS: Input status of each sensor (vehicle speed, gyro)

② In UBX-ESF-STATUS, the calibration status will transition from "NOT CALIBRATED" or "INITIALIZING" to "SUSPENDED" or "CALIBRATING" and then to "INITIALIZED" or "FUSION".
Uncalibrated: "NOT CALIBRATED" or "INITIALIGING"
During calibration: "SUSPENDED", "CALIBRATING"
Best condition: "FUSION", "INITILIZED", or "CALIBRATED"

③ If the Fusion Filter Mode in UBX-ESF-STATUS is displayed as "FUSION", the calibration has been completed successfully and the optimal positioning condition has been achieved.

UBX-ESF-STATUS screen (status transition)

Operational verification and log utilization

To ensure the dead reckoning (ADR) function of the EVK-M8L/M8U works properly, driving tests in a real vehicle environment are essential. By integrating IMU and vehicle signals with GNSS, highly accurate position estimation is possible even in situations where satellite signals are lost.
During the driving test, sufficient driving data, including left and right turns, must be collected to complete calibration of the sensor mount and alignment. The driving trajectory can be displayed on Google Maps or Earth to visually check the validity of the route and the progress of the calibration, and can also be used for accuracy verification and debug reports.

How to display on Google Maps/Earth

The logs obtained from the driving test can be displayed as driving tracks on Google Maps. First, play the log in u-center, then select "File" → "Database Export" → "Google Map Html" from the pull-down menu.
After selecting, save the file in a location of your choice. After playing the log in u-center, select "File" → "Database Export" → "Google Map Html" from the pull-down menu.

Instructions for creating UHtml files and driving log tracks on Google Maps

Just like Google Maps, the acquired log can also be displayed as a driving track on Google Earth. Double-click the created file (Kml) to launch Google Earth, and you can see that the log acquired during the driving test is displayed on Google Earth.

Procedure for creating kml files and driving log tracks on Google Earth

Log acquisition and analysis during test runs

During a test drive, unexpected behavior or positioning problems may occur. To analyze these, it is important to record and save the data during the test drive. Click the Debug button and then the Record button to add debug messages to the regular log. Adding debug messages will make analysis easier, so we recommend enabling it during test drives.

Record and Debug buttons used for debugging and post-test analysis, and a log confirmation screen

Common problems and how to deal with them

Positioning status is unstable

If the positioning is unstable during the driving test, please check the following items.
① Is the satellite configuration unbalanced? (Is the DOP value too high?)
② Are you receiving signals from the set satellites correctly?
3) Is the received signal level generally 40dB or higher?
④ Are there at least 3 to 4 satellites available?
⑤ Are the latitude, longitude, and altitude values correct?
⑥ Have you checked the positioning mode (3D fix)?

Items to check on u-center screen

Does not switch from 3D Fix to 3D+DR mode

If the mode does not switch from GPS independent positioning (3D Fix) to 3D+DR mode, please check that the vehicle speed pulse (WHEELTICK) from the vehicle is being input correctly. From the pull-down menu on u-Center, select "View" → "Table View", and in the Table View window, select "ESF-MEAS Single Tick" and click "+". "ESF-MEAS Single Tick" will be added to the window Index.

If no vehicle speed pulse is input from the vehicle, the value of ESF-MEAS Single Tick remains "blank" or "0.0" and does not change. In this case, the mode does not change from 3D Fix mode to 3D+DR mode.
If a vehicle speed pulse is being input from the vehicle, the ESF-MEAS Single Tick value will be incremented, and you will see the value gradually increase.Then, the system will transition successfully from 3D Fix mode to 3D+DR mode.

Summary: EVK-M8L/M8U improves development efficiency and accuracy

The EVK-M8L/M8U evaluation kit for u-blox's automotive GNSS products is a highly practical tool that can be used for everything from early development evaluations to driving tests, efficiently implementing GNSS into in-vehicle navigation systems. It is highly suitable for evaluation in real-world environments, as it can confirm stable positioning performance even in environments where GNSS signals are unstable, such as urban areas and tunnels. If you are considering using the EVK-M8L/M8U, please feel free to Inquiry Nexty Electronics.

Related information and Inquiry

Partnered Manufacturers: u-blox AG
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