Hector Trajectory path is not flowing smoothly

Question

I used the hector mapping package in combination with an XV-11 Vacuum Cleaner. Although its laser has a relatively low range and update rate, the created maps turned out to be pretty accurate, and much better than GMapping.

There is one small problem with displaying the trajectory though. The path it creates is correct for most of the time, but sometimes it determines the robot position wrongly, which results in a 'spiky' trajectory path. I attached an image for clarifying what I mean: http://imgur.com/npbAq1s

Does anyone have an idea where these erroneous positions come from, and how to solve the problem?

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Originally posted by AeroR on ROS Answers with karma: 11 on 2013-05-16

Post score: 1

Answer 1

Hi, very interesting to see things working so well with the XV-11, thanks for raising awareness of that :)

The fact that the map looks consistent clearly suggests that the internal state of the mapping system does not jump in as shown in your screenshots. It is thus very likely that your tf setup is messed up in some way (the trajectory server uses tf for generating the path displayed). You most likely have both hector_mapping generating a map->base_link transform as well as some other node doing the same (AMCL would be a candidate for example). When the trajectory server queries tf for transform data based on a timer, it more or less randomly gets one or the other, resulting in this jagged path. That at least is the most probable cause I see from looking at what you posted.

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Originally posted by Stefan Kohlbrecher with karma: 24361 on 2013-05-16

This answer was ACCEPTED on the original site

Post score: 3

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Original comments

Comment by AeroR on 2013-05-21:
Thank you for your answer! I looked at my transformation frames, and found out that both hector_mapping and my rosbag were publishing on the /odom topic. Depending on which source had last published onto the topic, the trajectory was either updated correctly or wrongly.

Comment by AeroR on 2013-05-21:
By the way, I solved this by removing all /odom entries from the rosbag file using the method described here: http://answers.ros.org/question/56935/how-to-remove-a-tf-from-a-ros-bag/