This includes an estimate of the covariance on the measurement. The GPS measurement should be provided on the / gps topic and should come in the form of an Odometry message. This modification, however, comes with a few requirements and caveats.ġ. So, the general launch procedure that we use looks likes so: Moreover, to make sure IMU measurements are applied in an absolute sense the parameter ‘ imu_absolute’ must also be set to true. The launch file for robot_pose_ekf now has a ‘gps_used‘ parameter that can be used to turn on the use of absolute measurements in the filter. So what’s it look like?Īctivating this feature in robot_pose_ekf is fairly simple. More information on using indoor positioning systems in ROS can be found here. Note, that an indoor positioning system can also provide absolute IMU measurements. These absolute measurements can come from your favourite GPS or from an indoor positioning system such as Vicon or Optitrack. However, any new GPS and/or IMU measurements are applied as absolute measurements of position. After this, it applies the wheel encoder and visual odometry data differentially.
Gps webots mod#
This mod works by initializing the filter at the first GPS and IMU measurement it receives, as opposed to the first wheel/visual odometry measurement as before. In order to achieve this, we forked the navigation repo and modified the main robot_pose_ekf node to incorporate absolute position measurements. While, robot_pose_ekf is mostly used as an odometry filter and therefore incorporates differential position estimates, we thought this was a good place to start incorporating some absolute position measurements.
Being absolute about position measurements This package is primarily used to probabilistically combine data from various sensors that provide odometry data (wheel encoders, cameras, IMU) using an extended Kalman filter. A natural place to start incorporating GPS is in the navigation stack, specifically robot_pose_ekf. As a field robotics company, Clearpath Robotics loves using GPS systems! However, ROS does not yet provide an effective method of incorporating GPS measurements into robots.
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