# H3 and S2 Hexagonal Cell Index Encoder and Neighbor Bridge

Encode lat/lng into Uber H3 hexagons (res 0-15) and Google S2 Hilbert cells (level 1-30) with index, id, token, quadkey, areas, k-ring neighbors, compaction, parent ladders and round-trip drift.

> Canonical page: https://elysiatools.com/en/tools/h3-and-s2-hexagonal-cell-index-encoder-and-neighbor-bridge

- **Category:** Geography

- **Keywords:** h3 index, s2 cell id, hilbert quadkey, quadkey bridge, h3 k ring, compact cells, lat lng to h3, s2 token

## Overview

Enter a coordinate, an H3 resolution (0-15) and an S2 level (1-30). The tool computes the Uber H3 index (base cell, center, boundary-derived area and max edge, parent ladder, gridDisk k-ring with optional compactCells compaction) and the Google S2 cell (Hilbert quadkey face/digits, exact 64-bit BigInt cell id, trimmed token, center, the four same-face quadtree neighbors), then bridges the systems: size-matched Web-Mercator/Bing quadkey, H3→S2 and S2→H3 conversions through cell centers, and round-trip drift in meters so you can see the quantization cost of switching systems.

## Inputs

- **Latitude** (number): 37.7796
- **Longitude** (number): -122.4194
- **H3 Resolution (0-15)** (number): 9
- **S2 Level (1-30)** (number): 14
- **K-Ring Radius (0-6)** (number): 1
- **Compact the k-ring cell set** (checkbox)

## When to use

- When designing spatial indexing and partitioning schemes across Uber H3 and Google S2 systems.
- When evaluating spatial precision loss and center drift when bridging coordinates between hexagonal and quadtree grids.
- When computing k-ring disk neighborhoods and hierarchical cell compaction for spatial storage optimization.

## How it works

- Enter a coordinate pair (latitude and longitude), select an H3 resolution (0–15), and set an S2 level (1–30).
- Specify an optional k-ring radius (0–6) and toggle compaction to calculate neighborhood expansions and reduced cell representations.
- The tool generates H3 indices, base cells, areas, and parent ladders alongside S2 64-bit BigInt IDs, hex tokens, Hilbert quadkeys, and same-face neighbors.
- Inspect the cross-grid bridge table comparing equivalent Web-Mercator quadkeys and measuring round-trip center drift in meters.

## Use cases

- Spatial indexing benchmarking: Compare cell boundary sizes, areas, and indexing representations between H3 hexagons and S2 cells.
- Ride-hailing and logistics optimization: Compute k-ring search radii and test compact cell representations for geo-fencing and dispatch areas.
- Cross-database geospatial interoperability: Translate location records between systems using S2 cell IDs and systems using H3 hexagonal indices.

## Frequently asked questions

### What is the difference between an H3 index and an S2 cell ID?

H3 uses a hierarchical hexagonal grid across 16 resolutions, whereas S2 projects Earth onto a cube subdivided using a Hilbert space-filling quadtree curve up to level 30.

### What does round-trip drift measure?

Round-trip drift measures the geographic distance in meters between original coordinates and the cell center after converting between H3 and S2 indexing schemes.

### How does k-ring cell compaction work?

Compaction replaces groups of fully contained child cells within a k-ring disk with their common parent cell at a lower resolution to reduce total index count.

### What is an S2 token?

An S2 token is a hexadecimal string representation of the 64-bit S2 cell ID with trailing zeros stripped for compact storage.

### Can I inspect higher-level parent cells for H3?

Yes, the tool outputs the parent ladder from resolution 0 base cells down to your target H3 resolution.

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