Distance of a line by camera points

Hello Everyone

I have a stereo camera,

I want to figure out the angle of an object with respect to ground.

Please see the attached image.

I know the length of the line lp, hp and bc. What I want to do is to figure out the angle bac. I know if I can find either ab or ac; I can use trigonometry to solve for angel bac. But please edify me for how can I find this.

Any suggestions or help is greatly appreciated.

[Matt J]

Do you have a camera image? And what do you know about the camera? Has it been calibrated? Do you know the intrinsics?

[arun Dhillon]

Yes the camera has been calibrated, I have calibrated the rgb lens of the camera using camera calibrator app of Matlab. Further the camera gives me the distance of the object from the camera i.e, I give in the coordinates that I want the distance for and it gives me how far that point is from the camera. I cannot produce the camera image right away, but the model that I presented above is what I want to solve for. The angel bac...

[Matt J]

It would be good if you showed the code you used to get the distances.

[arun Dhillon]

I am using the following code to get the distance from camera to any point.

https://github.com/IntelRealSense/librealsense/blob/master/wrappers/matlab/depth_example.m

[Matt J]

I see no distance calculations in that code. The function there doesn't even return anything.

[arun Dhillon]

The camera that I am using is Intel D435i, and to get the distance you have to use the following line of code.

depth.get_distance(x,y) %x,y are coordinates of the point that I wanna get distance for..

Answer 1

[Matt J]

Well, I have no familiarity with the 3rd party Github library that you're using. However, it is a stereo camera class. So, it should offer you methods not just to calculate "depth", but the actual real-world coordinates of points in the image. Matlab's own stereo vision routines do offer such things

https://www.mathworks.com/help/vision/ref/triangulate.html#buefm11-1-stereoParams

https://www.mathworks.com/help/vision/ref/reconstructscene.html

Once you have the 3D coordinates of a,b, and c, you can of course calculate anything.