atpol100k               atpol100k creates ATPOL grid 100km x 100km and
                        returns it as sf object
atpol10k                atpol10k returns ATPOL grid 10x10 km and
                        returns it as sf object
atpol1k                 atpol1k creates ATPOL grid 1km x 1km and
                        returns it as sf object
atpol_div               atpol_div creates ATPOL grid divided by 2, 4 or
                        5 (based on divider parameter) and returns it
                        as sf object. Useful for grids like 5 x 5 km
                        (divider = 2), 250 x 250 m (divider = 4) or 20
                        x 20 m (divider = 5). For details see Verey and
                        Komsta (2018)
boundaryPL              boundaryPL reads the file data/pl_boundary.Rds
                        with simplified boundary geometry.
check_atpol_square      Reverse engineering of published ATPOL grids
grid_to_latlon          grid_to_latlon converts the ATPOL grid to
                        latitude and longitude. With 'xoffset = 0' and
                        'yoffset = 0' parameters it returns coordinates
                        of the upper left corner of the grid.
latlon_to_grid          latlon_to_grid(lat, lon, length) converts
                        geographical coordinates to ATPOL grid of given
                        length
plotPoitsOnAtpol        plotPoitsOnAtpol() plots the observations on
                        ATPOL 10km x 10km grid
