a5_migrate: Migrate cell ids from the pre-1.0 index

In a5R: 'A5' Discrete Global Grid System

Migrate cell ids from the pre-1.0 index

Description

Converts cell ids written by a5R before 1.0 (the a5 Rust crate 0.10 and earlier, the "v0" index) to the current, permanent index. A5 1.0 threads its space-filling curve through the cells differently, so cells keep their shape and position but get new ids. The conversion is a cheap bit operation; there is no need to re-index data from its coordinates. The exception is resolution 1, whose 60 cells changed from triangles to pentagons: each migrated resolution-1 id is the new cell containing the old cell's centre.

Usage

a5_migrate(cell)

Arguments

cell	An a5_cell vector of ids in the v0 index.

Details

A v0 id is still a valid cell in the current index, but in a different place, and nothing in the id records which version wrote it. Migrate stored ids exactly once, as soon as they are read: migrating current ids, or migrating twice, gives wrong cells without any error.

Upstream will retire this conversion in a future version.

Value

An a5_cell vector of the same cells in the current index, the same length as cell. NA where cell is NA.

See Also

a5_cell_from_arrow() to read stored ids.

Examples

# A resolution-8 cell id from a5R 0.6.0
v0 <- a5_cell("59c4780000000000")
a5_migrate(v0)

a5R documentation built on Oct. 19, 2026, 5:08 p.m.