pause and resume the mapping by using the finish_trajectory service

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lwang

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Nov 21, 2016, 9:08:33 AM11/21/16
to google-cartographer
Hi there,
First, thanks for your incredible work!
I was working on a turtlebot 2 robot with rgb depth camera, I tested the cartographer algorithm using the cartographer_turtlebot package
I learned from this post: https://groups.google.com/forum/#!topic/google-cartographer/ph_QjRXxP_g and the git pull: https://github.com/googlecartographer/cartographer_ros/pull/151 that we can use the finish-trajectory to pause and resume the map.
When I called the finsh_trajectory service, I got a map saved to disk and the node was shutdown, but how should I resume the map based on the saved map?
Is it possible to pass the saved map to a newly started node and expand the map?

Best regards, Longxiang 

Damon Kohler

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Nov 25, 2016, 2:54:25 AM11/25/16
to lwang, google-cartographer
Hi Longxiang,

Pause and resume only works in memory right now. There's no serialization of the SLAM problem to allow you to resume from a saved map.

What currently works is:

- Start mapping
- Call /finish_trajectory to save an intermediate state
- Continue mapping

Calling /finish_trajectory will stop the current trajectory and start a new one. The two trajectories will be optimized together. In its current form, this may be useful for a robot that experiences an interruption in sensor data.

Hope that helps!
Damon

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Yutaka Takaoka

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Dec 10, 2016, 2:01:39 AM12/10/16
to Damon Kohler, lwang, google-cartographer
Hi Damon,

I saw calling /finish_trajectory stopped the current trajectory and started a new one.
However in terms of coordinate the new trajectory did not start from where the previous trajectory ended.
It seemed to start from zero point.
So that broke the consistency of the map.

Is it a proper behavior?

Thanks,
Yutaka



On Thu, Nov 24, 2016 at 11:54 PM, 'Damon Kohler' via google-cartographer <google-ca...@googlegroups.com> wrote:
Hi Longxiang,

Pause and resume only works in memory right now. There's no serialization of the SLAM problem to allow you to resume from a saved map.

What currently works is:

- Start mapping
- Call /finish_trajectory to save an intermediate state
- Continue mapping

Calling /finish_trajectory will stop the current trajectory and start a new one. The two trajectories will be optimized together. In its current form, this may be useful for a robot that experiences an interruption in sensor data.

Hope that helps!
Damon
On Mon, Nov 21, 2016 at 3:08 PM lwang <wlongxi...@gmail.com> wrote:
Hi there,
First, thanks for your incredible work!
I was working on a turtlebot 2 robot with rgb depth camera, I tested the cartographer algorithm using the cartographer_turtlebot package
I learned from this post: https://groups.google.com/forum/#!topic/google-cartographer/ph_QjRXxP_g and the git pull: https://github.com/googlecartographer/cartographer_ros/pull/151 that we can use the finish-trajectory to pause and resume the map.
When I called the finsh_trajectory service, I got a map saved to disk and the node was shutdown, but how should I resume the map based on the saved map?
Is it possible to pass the saved map to a newly started node and expand the map?

Best regards, Longxiang 

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Damon Kohler

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Dec 12, 2016, 4:08:52 AM12/12/16
to Yutaka Takaoka, lwang, google-cartographer
Currently, /finish_trajectory only finishes the current trajectory and starts the next one. After that, global localization takes over to connect the two trajectories.

It's not working very well in 3D, currently. Though we know what's missing to improve the results in both 2D and 3D.

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