Why odom/filtered output on map frame is moving?

Question

Hello, im working on a navigation system.

I am using two instances of ekf filter from robot_localization package. I am obteinig that in the "odom" frame, i receive the gps signal with the odometry_map signal with a good performance, the signals are near enough to the robot whe it is static.

But when i visualice what is happening in the "map" frame, the robot is constantly moving around the ground, and the gps, and the /odometry/global signals are moving together with the robot.

So, the idea that i have is that the "odom -> map" trasnform frame is constantly moving alone. Why i am getting that? Is it becuase the GPS signal ? I am watching that sometimes the robot move in a area that more than 3m of error, which is usually the average gps error.

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Originally posted by Johart24 on ROS Answers with karma: 3 on 2022-03-14

Post score: 0

Answer 1

This is normal behavior if you configured it according to the documentation.

Idea is that local EKF handles wheel odometry and IMU to provide continuous vehicle trajectory (odom->base transform). Global EKF takes global position from GPS and uses it to provide map->odom transform. This can (and most probably will) jump around due to GPS inaccuracies.

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Originally posted by Nikodem with karma: 61 on 2022-03-14

This answer was ACCEPTED on the original site

Post score: 1

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Original comments

Comment by Johart24 on 2022-03-14:
Hey thanks for answer. I have a concern. If i want to publish a gps coordinate waypoint, this inaccuracies in the map_frame are gonna interfere on the trajectory path creation?

Comment by Johart24 on 2022-03-14:
I share you a capture of how it looks like. https://ibb.co/D5Jv1tZ