Sensors Stack 2025

Clone this repo into src directory.

If your looking for the nav/sensors onboarding go here instead: https://github.com/umigv/sensors-onboarding

Follow the installation here to get dependinces:

https://www.stereolabs.com/docs/ros2

Usage:

(Assuming we already have everything installed)

Check if your GNSS module is detected:

ls /dev/tty*

You should see /dev/ttyACM0. To verify the raw GNSS data stream:

cat /dev/ttyACM0  # No sudo required

The output should look something like this:

$GNGSA,A,1,,,,,,,,,,,,,99.99,99.99,99.99,1*33
$GPGSV,1,1,00,0*65
$GNRMC,082019.00,V,,,,,,,230623,,,N,V*1D

To start up the gpsd daemon:

gpsd -nG -s 115200 /dev/ttyACM0

By default, gpsd runs as a systemd service (systemctl start gpsd), meaning it’s managed automatically as a daemon. However, for USB GNSS modules, this setup can be unreliable—sometimes the service starts before the module is detected, or it may not restart properly.

To avoid these issues, it’s better to start the daemon manually instead of relying on systemd. Since we still want gpsd to start at boot, we can set up a cron job that runs the command automatically when the system starts.

Then we can check if the GPS and gpsd is working using this command that displays GNSS and satellite data via a GUI:

xgps

⚠️ Warning: It may take several minutes for the GNSS module to acquire a GPS fix, especially in areas with poor satellite visibility. Ensure you are in an open area with a clear view of the sky for faster results. On cold start (No prior data), it can take around 3-5 minutes in open areas (longer in poor conditions).

Running the Sensors Stack

1. Open 2 terminals.
2. cd ~/ros2_ws in each terminal.
3. run source /opt/ros/humble/setup.zsh && source install/setup.zsh in each terminal.
4. Terminal 1: ros2 launch ublox_gps gnss_test.launch.py
5. Terminal 2: ros2 launch zed_wrapper zed_camera.launch.py camera_model:=zed2i

Installation and Setup

Install GPSD

The simplest way to retrieve GNSS data on Linux is by using gpsd, a service daemon that handles GNSS data and provides easy API access. 7. Open new terminal. 8. run: source /opt/ros/humble/setup.bash 9. run: source install/setup.bash 10. run: ros2 launch marvin_bot_description teleop_launch.py

This guide walks you through setting up your GNSS with the ZED SDK’s Global Localization module. While the instructions focus on the Ublox ZED F9P GNSS module, they should also apply to other GNSS modules.

Installation

The simplest way to retrieve GNSS data on Linux is by using gpsd, a service daemon that handles GNSS data and provides easy API access.

Installing gpsd from source ensures you have the most recent stable version.

# Install dependencies
sudo apt update && sudo apt install scons libgtk-3-dev

# Clone and compile gpsd
git clone https://gitlab.com/gpsd/gpsd.git
cd gpsd && git checkout 8910c2b60759490ed98970dcdab8323b957edf48
sudo ./gpsinit vcan
scons && scons check && sudo scons udev-install

# Add Python path for gpsd tools
echo 'export PYTHONPATH="$PYTHONPATH:/usr/local/lib/python3/dist-packages"' >> ~/.bashrc

Granting Permissions

To allow gpsd to run without root privileges, add your user to the necessary groups:

sudo adduser $USER dialout
sudo adduser $USER tty

Log out or reboot for changes to take effect.

Verifying GNSS Module Detection

Check if your GNSS module is detected:

ls /dev/tty*

You should see /dev/ttyACM0. To verify the raw GNSS data stream:

cat /dev/ttyACM0  # No sudo required

The output should look something like this:

$GNGSA,A,1,,,,,,,,,,,,,99.99,99.99,99.99,1*33
$GPGSV,1,1,00,0*65
$GNRMC,082019.00,V,,,,,,,230623,,,N,V*1D

Running gpsd

By default, gpsd runs as a systemd service, but USB GNSS modules may work better if gpsd is started manually.

Starting gpsd Manually

gpsd -nG -s 115200 /dev/ttyACM0

Replace /dev/ttyACM0 with your actual GNSS device port.

Starting gpsd at Boot

To automatically start gpsd at boot, add the following cron job using:

crontab -e

Add the following line to the file you're editing (with vim/nano/whatever you prefer)

@reboot sleep 10 && /usr/local/sbin/gpsd -nG -s 115200 /dev/ttyACM0

Then we check if gpsd is working properly using the graphical xgps tool:

xgps  # Displays GNSS and satellite data in a GUI

Running the Sensors Stack

1. Open 2 terminals.
2. cd ~/ros2_ws in each terminal.
3. run source /opt/ros/humble/setup.zsh && source install/setup.zsh in each terminal.
4. Terminal 1: ros2 launch ublox_gps gnss_test.launch.py
5. Terminal 2: ros2 launch zed_wrapper zed_camera.launch.py camera_model:=zed2i