Question about monocular camera and RTAB-Map for Android

[marius851000bis]

Hello. I've (some day ago) discovered the possibility offered by the SLAM technique. I'm interested in the potential of SLAM for doing indoor mapping for OpenStreetMap (mostly room scale with point of interest), where I can't use both GPS and imagery. As I don't have any stereo or RGBD camera I could get to work with RTAB-MAP (The 3ds video recording seem to generate invalid calibration, and can't be used), I've seen RTAB-MAP for android. After figuring I should compile it myself (and compile it via docker, disabling memory usage check with seemingly no issue and adding the possibility to filter point with a max distance of 10m). While I'm sad I have to use a proprioritary Google's library, it work relatively good compared to what I expected. I however have two question :

(I use lineageOS, with MicroG and Google's ARCore installed from PlayStore)

Why can't I regenerate cloud ?

I try to regenerate point cloud from my recording, so I can open it with another software that would offer a top-down image with alpha (don't know which software permit this), I have error log that have things like "Cloud 156 not found in cache!". (I finally took a screenshot of the top-down ortho projection, and it worked).

 Is there a better (free) software adapted to my need ?

That is, indoor 3d point cloud generation from monocular video. Photogrammetry perform worse for closed environment, and are slow.

I also did some small scale test for using point cloud for editing outside openstreetmap :

It allowed to have a greater precision for placing element, with great precision, but aerial imagery provided by the government are pretty good too where I live, so this isn't usually a good idea compared to the time it take to generate the point cloud.

But it allowed me to place precisely the bench that was under a tree. I haven't yet had time to fully test it indoor (broke it while replacing the front glass today).


Thank.

[matlabbe]

Hi,

In general with single RGB camera, photogrammetry (Meshroom) can be used but with some limitations as you referred. rtabmap for android can create a mesh from the tracked points for ARCore, this works only if there are enough visual features in the environment, and it will interpolate in textureless areas. See example from 8:45 in this video https://www.youtube.com/watch?v=rVpIcrgD5c0&t=240s (it is from ARKit but the same can be done from android version).

cheers,
Mathieu