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cartographer-project / cartographer_ros

Provides ROS integration for Cartographer.
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Push broom 2D LIDAR #810

Closed davidromanos closed 6 years ago

davidromanos commented 6 years ago

Hi, one very short issue.

A bit of background here: I am trying to use cartographer outdoors. My system is a golfcart with a LIDAR placed at a knee high approximately. The LIDAR is a Sick LMS151 with operating range: 0.5 m - 50 m (Max. range with 10 % reflectivity: 18 m). I am trying to map parts of my university campus, i.e. streets, parking lots and others. To do so I use IMU measurements as well, but the results don't look good.

The actual issue: To get more information of the environment it seemed a good idea to use a tilted LIDAR (push broom configuration) placed on the roof of the golfcart. I've seen that the 2D public data supplied in http://google-cartographer-ros.readthedocs.io/en/latest/data.html includes push broom LIDAR data but I have some doubts with respect to cartographer and this configuration:

Thanks in advance for your help!

p.s.: I managed to get good results with only horizontal LIDAR indoors but not with the push broom LIDAR. Find here a picture of the golfcart with the aforementioned configuration.

gaschler commented 6 years ago

Can I use cartographer with a push broom configuration LIDAR (obviously with the correct tf)?

In principle, yes. However, for good quality, you need to scan all directions and see more features than just a hilly ground.

In such case, should I use MAP_BUILDER.use_trajectory_builder_2d = true or MAP_BUILDER.use_trajectory_builder_3d = true?

If you have 2D lidars, you can only use the first config.

Can I use both range data from the horizontal LIDAR and the push broom LIDAR?

Sure, you can have multiple lidars.

davidromanos commented 6 years ago

Thanks for the quick reply @gaschler ! What do you mean by "scan all directions"? The push broom LIDAR is a Sick TIM551 with operating range: 0.05 m to 10 m (Max. range with 10 % reflectivity: 8 m ) and the aperture angle is limited between 0° and 180°. Furthermore, both LIDARs are not multi echo lasers.

You say in principle I can use cartographer with a push broom LIDAR but, do you think I can get good quality with this configuration and considering I want to map regular urban outdoor environments?

I really appreciate your help thanks!!

gaschler commented 6 years ago

180 degrees aperture is really on the lower end (because it will bias local scan matching).

10 meters range is probably not enough for outdoor because you need to see something in scan matching.

gaschler commented 6 years ago

Closing for inactivity, feel free to post when there is something new.