How to find the minimal distance between the robot and an object (chair) using point clouds? [closed]

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Hello

I would like to do some analysis during the runs of my platform. My platform has laser, IMU, Kinect and encoders. So Im trying to program a node that can gives the distance between the object(chair) and the platform while performing a parking. I would like to use the PCL library but never worked with depth images before. So I would like to do a parallel parking between two chairs so the robot(my platform which can be assumes is quadratic) is parked between two chairs.So Im trying to get the minimal distance between the chair and the platform when is parked between them. Any help or examples of some code with point clouds and depth images regarding to distances to the objects??

Thanks