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S2Decoder

From-v4.0

caution

This module is still experimental. It may have issues and functionality may change in minor releases.

Overview​

S2 is a discrete global grid system built on the Hilbert curve. See s2geometry.io for more information.

The S2 functions in math.gl are currently focused on decoding S2 encoded data, not encoding it.

API Notes​

The API provided by this module works with S2 token strings, as those are typically found in data files.

S2 cells have multiple representations, and can be represented as:

  • S2 token strings (stringified versions of the indexes)
  • S2 indexes which are 64 bit numbers represented by JavaScript bigint

The 64 bit index layout allocates 3 bits for the face id and 60 bits for the Hilbert curve position. The least significant bit is always set and trailing zero bits encode the level. When expressed as hexadecimal strings these trailing zeros are omitted; such a string is known as the S2 token. An empty cell is represented by the token X.

S2Decoder​

S2Decoder implements the DGGSDecoder API:

  • cellColumnNames: ['s2', 's2Token', 's2_token', 's2Cell', 's2_cell', 's2CellId', 's2_cell_id']
  • tokenToCell(token: string): bigint
  • cellToToken(cell: string | bigint): string
  • cellToLngLat(cell: string | bigint): [number, number]
  • cellToBoundary(cell: string | bigint): [number, number][]
  • cellToBoundaryFlat(cell: string | bigint): number[]
  • cellToBounds(cell: string | bigint): Bounds2D