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cartographer-project / cartographer

Cartographer is a system that provides real-time simultaneous localization and mapping (SLAM) in 2D and 3D across multiple platforms and sensor configurations.
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why two lidars? #212

Closed sunmk2006 closed 7 years ago

sunmk2006 commented 7 years ago

2D mapping only need one horizontal lidar,but your bag data always have another vertical_laser_2d,why?

wohe commented 7 years ago

You're correct that 2D mapping only needs the horizontal LIDAR, and you can ignore the vertical LIDAR in this case.

Regarding the vertical LIDAR: Why not? We collected the data, so we put it in the bags. One use case would be to reconstruct geometry for which the horizontal LIDAR is not suitable since it mostly covers a single plane, if you ignore the fact that the backpack is not always perfectly level. Of course you are free to find other uses.

sunmk2006 commented 7 years ago

Did you have use the vertical lidar data in the 2D mapping process?Can be done with 2D laser reconstruction？

wohe commented 7 years ago

I'm not sure I understand your questions. To run 2D SLAM, you do not need the vertical LIDAR, e.g. running

roslaunch cartographer_ros offline_backpack_2d.launch bag_filenames:=${HOME}/Downloads/cartographer_paper_deutsches_museum.bag

does not make use of it. You can make use of it though, e.g. using the SLAM result from above and running

roslaunch cartographer_ros assets_writer_backpack_2d.launch bag_filenames:=${HOME}/Downloads/cartographer_paper_deutsches_museum.bag trajectory_filename:=${HOME}/Downloads/cartographer_paper_deutsches_museum.bag.pb

computes X-ray images using both LIDARs and stores the results at ~/.ros/xray_* by default.

sunmk2006 commented 7 years ago

3D mapping you have tow lidars, Can I use a tilted laser to mapping,(eg. A Velodyne VLP-16 lidar with a tilt of 45 degrees)to get trajectory and reconstruction?

SirVer commented 7 years ago

3D mapping you have tow lidars, Can I use a tilted laser to mapping,(eg. A Velodyne VLP-16 lidar with a tilt of 45 degrees)to get trajectory and reconstruction?

​​Answered here: https://github.com/googlecartographer/cartographer/issues/213