1. A method for detecting an opening in a structure represented by a three-dimensional point cloud, said method comprising: creating a three-dimensional point cloud map of a scene, said three-dimensional point cloud map comprising a plurality of points representing a ground plane and said structure upon said ground plane; rotating said three-dimensional point cloud map to align said plurality of points representing said ground plane with a reference plane of a delimiting volume; converting said plurality of points representing said ground plane and said structure to a plurality of voxels, said plurality of voxels forming a voxel grid representing said three-dimensional point cloud map; forming a plurality of voxel strips, each voxel strip being defined by a grouping of aligned voxels; determining whether each voxel strip of said plurality of voxel strips comprises a ground voxel and a ceiling voxel; and determining whether an absence of said voxels defined between said ground voxel and said ceiling voxel represents said opening in said structure.