Symmetry of atomic layers as well as symmetry of mosaics, lattice designs, symmetry of electron diffraction patterns or any pattern with two-dimensional periodicity can be classified by their symmetry groups. For comparative studies of crystallographic structures the finer methods of classification / description are more appropriate (for example: "circle packings" -Niggli , "isohedral tilings" - Sinogowitz, "lattices complexes" - Niggli, "crystallographic orbits" - Wondratschek"). All these concepts are related with a set of symmetry equivalent points (G-orbit). The orbits are visualised as "crystallographic mosaics" (by connection of the closest points of the orbit), they can be characterised by Shubnikov or Laves nets and there always exists a number (circle packing density or shortly CPD) that is related to a given orbit. The CPD function introduced by the author and specially its contour map is a good frame for locating symmetry elements, asymmetric units or points with higher plane symmetry into a unit cell. Some conclusions relating the position of an atom in the unit cell and their dimension can also be drawn. The properties and constructions of CPD contour maps for all 17 plane groups will be given in this work.

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