Can we use two two-dimensional lasers as a three-dimensional laser?

[sunmk2006]

A two-dimensional laser placed horizontally and a two-dimensional laser placed vertically constitute a data acquisition device, which can obtain both horizontal and vertical data. If we convert the two data into the form of point clouds, can we use them as input data of slam 3d cartographer?

[kdaun]

~~Yes, Cartographer supports the use case of using two 2D Lidars as input for the 3D SLAM pipeline. We use a similar setup for our mapping backpack. See the backpack_3d launch and configuration files. Demo instructions are available in the demo documentation.~~ [Correction] Cartographer will accept two 2D LiDARs as input for the 3D pipeline, but in our experience the quality of the localization and the map is strongly degraded in comparison to using 3D LiDARs.

[sunmk2006]

Can you specify which configuration file uses two two-dimensional lasers as input for 3Dslam input? Does the backpack_3d launch file use two 3D Lidars ?

[kdaun]

See backpack_3d.launch and backpack_3d.lua. In our case we are using two multi-line LiDARs. Depending on your system setup using two 2D LiDARs might work as well. Although, I have limited experience here.

[sunmk2006]

I have done this already, but the result is not good. Can you help me look at it? the config file and the bag file is b0-2014-07-11-10-58-16.bag

[kdaun]

Ok, with only two 2D LiDARs there is not enough overlap between the scans and the mapped area to accurately resolve the 6D pose. Therefore, the quality of the map is degraded. Reducing the resolution might lead to somewhat better matches as there should be more overlap between the scans and the map. To gain a high quality 3D map with full 6D pose estimation with Cartographer 3D LiDARs are needed.