Hierarchy

Hex cells cannot be truly hierarchical since no combination of hexagons makes a larger hexagon. e.g. H3 defines a parent hex by taking a vertex from each of the k-ring 1 cells. This means a point in a cell may not actually be contained by the parent cell. BEAHIV doesn't claim to be hierarchical, but has some functionality to move between resolutions.

Parents

Parent are overlapping cells that are exactly twice the side_length. Each cell has either one exclusive (when ||(q, r||) both even) or two shared parents. Exclusive parents have the same centroid. get_parent will return the exclusive parent (if there is one); get_parents returns one or both.