title: hwo to use pcl to achieve that discretizing the 3D point cloud into a 2D grid over the xy plane, not use the voxelgrid?
body: <p>I want to project the 3D point cloud into a 2D grid over the xy plane, each grid cell size is 20cm*20cm, how to achieve it effectively?</p>
  
  <p>NOT use VoxelGrid method, because I want to retain every point and deal with them in the next step(Gaussian kernel every column and use EM to deal with each grid)</p>