RTK Positioning

Hardware

The AutomatePro offers an optional RTK GNSS position sensor, giving it cm level positional accuracy. This is based on the Ublox F9P and R series devices and includes positional accuracy down to 2.5cm. If the option is included there will be a blue FAKRA connector for which the antenna can be connected to. "GNSS-2" is used for the position and "GNSS-1" is used for heading.

GNSS Position Specifications

Parameter	Value
Receiver	Ublox F9P or F9R (see Wheel Speed & Direction Input)
Connector	GNSS-2 (FAKRA C - Signal Blue)
Supported Constellation	GPS, Galileo, BeiDou, GLONASS
Positional Accuracy	Down to 1cm 1. Using Ublox point perfect correction <6cm
Max Navigation Update Rate	Default 1Hz (Can be configured up to 7Hz)

Info

¹ Depends on antenna, distance to base station or correction serivce - see the receiver datasheet for more information

External Antenna

The AutomatePro system is compatible with a variety of multi-band high precision GNSS antennas that have a FAKRA Type C connector (Signal Blue). To find more information on the antennas that have been used with AutomatePro, this can be found here

Wheel Speed & Direction Input

The AutomatePro provides options for both wheel speed and direction input for applications requiring dead reckoning.

Connection Details

Pin Name & Number	Function	Description
WHEEL TIC / PIN 51	Tachometer input	5-24VDC input range (with respect to the common GND)
WHEEL DIR / PIN 52	Wheel rotation direction input	5-24VDC input range (with respect to the common GND)

Connector

Development Breakout Board

Important

This is a non-standard option - contact lemvos for more information

ROS API

Node: automatepro_gnss_position_node

Publishers

Topic	Type	Description
/sensor/gnss/position/fix	sensor_msgs/msg/NavSatFix	GNSS Position data (navigation satellite fix)
/sensor/gnss/position/fix_velocity	geometry_msgs/msg/ TwistWithCovarianceStamped	Velocity in local ENU frame.
/sensor/gnss/position/navposecef	ublox_msgs/msg/NavPOSECEF	GNSS Position in ECEF (Earth-centered, Earth-fixed coordinate system) format
/sensor/gnss/position/mon_hw	ublox_msgs/msg/MonHW	Hardware and Firmware status of the GNSS position module
/sensor/gnss/position/nmea	nmea_msgs/msg/Sentence	Raw NMEA messages
/diagnostics	diagnostic_msgs/msg/ DiagnosticArray	GNSS position ROS driver Diagnostics

Subscribers

Topic	Type	Description
/sensor/gnss/correction	rtcm_msgs/msg/Message	RTCM or SPARTN Correction data

Parameters

Parameter	Type	Values	Runtime R/W	Description
device	string	/dev/ttyACM0	read-only	Serial port (automatically configured)
frame_id	string	gnss_position	read-only	Frame id for the messages published
publish.all	bool	true/false	read-only	Publish all the messages
publish.mon.hw	bool	true/false	read-only	enable GNSS module diagnostics publishing
publish.nav.relposned	bool	true/false	read-only	enable NavRELPOSNED9 msg publishing set to false
publish.nav.heading	bool	true/false	read-only	enable heading publishing set to false
publish.nmea	bool	true/false	read-only	enable NMEA msg publishing
debug	int	0-4	read-only	0 - no debug msgs, 4 - all debug msgs

Configuration

Driver: automatepro_gnss_driver
Container: automatepro-core-driver

info

All the configuration related files can be found at /automatepro/config/ros directory.
These files will be mounted to docker container and will be used by the ROS driver.

config file can be found here.

~/.automatepro/config/ros/gnss_position_params.yaml

ROS Configuration

automatepro_gnss_position_node:
  ros__parameters:
    debug: 0 

    device: /dev/ttyACM0
    frame_id: gnss_position

    config_on_startup: false   

    # Publishers
    publish:
      all: false
      mon:
        hw: true
      nav:
        all: false
        posllh: false
        posecef: true
        relposned: false
      nmea: true

Important

Restart the automatepro-core-driver docker container after changing the configuration.
Configurations will only be applied after the container restarts.

docker restart automatepro-core-driver

Device Configuration

This section describes the configuration of the GNSS device. To explore the capabilities of the GNSS device, refer to the ublox documentation for more details.

You can use the pygpsclient GUI tool to configure the GNSS device. The video below demonstrates how to configure the GNSS device using the pygpsclient tool. Here is the configuration interface reference:

1. Changing the navigation rate
2. Changing the satellite preferences
3. Changing the GNSS mode

Example

Example code snippets to read GNSS position data from the /sensor/gnss/position/fix topic.

Python

import rclpy
from rclpy.node import Node
from sensor_msgs.msg import NavSatFix

class GNSSPositionSubscriber(Node):

    def __init__(self):
        super().__init__('gnss_position_subscriber')
        self.subscription = self.create_subscription(
            NavSatFix,
            '/sensor/gnss/position/fix',
            self.listener_callback,
            10)

    def listener_callback(self, msg):
        self.get_logger().info('Latitude: %f' % msg.latitude)
        self.get_logger().info('Longitude: %f' % msg.longitude)
        self.get_logger().info('Altitude: %f' % msg.altitude)

def main(args=None):
    rclpy.init(args=args)
    node = GNSSPositionSubscriber()
    rclpy.spin(node)
    node.destroy_node()
    rclpy.shutdown()

if __name__ == '__main__':
    main()

Run the node using the following command:

ros2 run automatepro_python_tutorials gnss_position_node

C++

#include <rclcpp/rclcpp.hpp>
#include <sensor_msgs/msg/NavSatFix.hpp>

class GNSSPositionSubscriber : public rclcpp::Node
{
public:
    GNSSPositionSubscriber()
        : Node("gnss_position_subscriber")
    {
        subscription_ = this->create_subscription<sensor_msgs::msg::NavSatFix>(
            "/sensor/gnss/position/fix",
            10,
            std::bind(&GNSSPositionSubscriber::listener_callback, this, std::placeholders::_1));
    }

private:
    void listener_callback(const sensor_msgs::msg::NavSatFix::SharedPtr msg)
    {
        RCLCPP_INFO(this->get_logger(), "Latitude: %f", msg->latitude);
        RCLCPP_INFO(this->get_logger(), "Longitude: %f", msg->longitude);
        RCLCPP_INFO(this->get_logger(), "Altitude: %f", msg->altitude);
    }
    rclcpp::Subscription<sensor_msgs::msg::NavSatFix>::SharedPtr subscription_;
};

int main(int argc, char *argv[])
{
    rclcpp::init(argc, argv);
    auto node = std::make_shared<GNSSPositionSubscriber>();
    rclcpp::spin(node);
    rclcpp::shutdown();
    return 0;
}

Run the node using the following command:

ros2 run automatepro_cpp_tutorials gnss_position_node