FastH3.jl

A pure Julia implementation of Uber's H3 hexagonal hierarchical geospatial indexing system.

Overview

FastH3.jl provides a complete, dependency-free Julia implementation of the H3 library. It maps latitude/longitude coordinates onto a hierarchical grid of hexagonal (and pentagonal) cells, enabling efficient spatial indexing, neighbor traversal, and distance computation.

Key properties:

• Pure Julia — no C dependencies or binary wrappers.
• Zero-allocation scalars — core index operations allocate nothing on the heap.
• Full H3 v4 API — covers indexing, inspection, traversal, hierarchy, directed edges, vertexes, and measurement functions.
• Callback overloads — many multi-result APIs also support op-first enumeration without allocating the result Vector; see Callback enumeration.

Quick Start

using FastH3

lat, lng = 0.6518070561696664, -1.7453292519943295  # radians
err, cell = latLngToCell(LatLng(lat, lng), 5)
err, center = cellToLatLng(cell)
err, disk = gridDisk(cell, 1)

C API Correspondence

Every public function in FastH3.jl corresponds to a function in the H3 C library. Docstrings include direct links to the matching C API documentation page.

Module

FastH3

Contents

• Callback enumeration (no result vectors)
• • APIs with callback overloads
  • getIcosahedronFaces and the vector form
  • What does not have a callback overload yet
  • See also
• Indexing
• Inspection
• • Index Properties
  • String Conversion
  • Error Descriptions
  • Types
• Traversal
• • Grid Disk
  • Grid Distance and Paths
  • Local IJ Coordinates
  • Neighbor Detection
• Hierarchy
• • Parent / Child Navigation
  • Compact / Uncompact
  • Resolution 0 and Pentagons
• Directed Edges
• Vertexes
• Measurement
• • Great Circle Distance
  • Unit Conversion
  • Average Hexagon Area
  • Average Edge Length
  • Cell Count
  • Exact Cell Area
  • Exact Edge Length