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Hierarchy

The A5 tiling system supports subdividing the world all the way from the 12 dodecahedron faces at resolution 0 to milimeter-scale leaf cells.

The cells are arranged in a logical hierarchy, with each cell having an integer resolution. Each cell has exactly 4 child cells, at the next resolution level, and one parent cell at the previous resolution level.

Naturally the 12 resolution 0 cells, representing the dodecahedron faces, have no parent and similarly leaf cells no children.

getResolution​

Returns the resolution of an A5 cell

function getResolution(index: bigint): number;

Parameters​

  • index (bigint) A5 cell identifier

Return value​

  • (number) The resolution level of the cell

cellToParent​

Returns the parent cell of an A5 cell.

function cellToParent(index: bigint, parentResolution?: number): bigint;

Parameters​

  • index (bigint) A5 cell identifier
  • parentResolution (number, optional) By default one level coarser than input resolution.

Return value​

  • (bigint) The parent cell identifier

cellToChildren​

Returns the child cells of an A5 cell.

function cellToChildren(index: bigint, childResolution?: number): bigint[];

Parameters​

  • index (bigint) A5 cell identifier
  • childResolution (number, optional) By default one level finer than input resolution.

Return value​

  • (bigint[]) Array of child cell identifiers

getRes0Cells​

Returns resolution 0 cells of the A5 system, which serve as a starting point for all higher-resolution subdivisions in the hierarchy.

function getRes0Cells(): bigint[];

Return value​

  • (bigint[]) Array of 12 A5 cell identifiers

Example​

import { getRes0Cells, cellToChildren } from 'a5-js';

const res0Cells = getRes0Cells();
const res1Cells = res0Cells.flatMap(cell => cellToChildren(cell, 1))