Introduction to IGEO7
IGEO7 is a hierarchically indexed hexagonal equal-area Discrete Global Grid System (DGGS) with the Z7 indexing system.
It is the equal-area alternative to H3, sharing the aperture 7 hexagonal hierarchy and a comparable 64-bit integer indexing of H3, but using the ISEA (Icosahedral Snyder Equal Area) projection instead of H3's gnomonic projection. This guarantees all cells have truly equal area (H3 cells vary by up to ±50%).
IGEO7 is described in: Kmoch, A., Sahr, K., Chan, W.T., Uuemaa, E. (2025). IGEO7: A new hierarchically indexed hexagonal equal-area discrete global grid system. AGILE: GIScience Series, 6, 32. https://doi.org/10.5194/agile-giss-6-32-2025
What is a DGGS?
A Discrete Global Grid System partitions the entire surface of the Earth into a finite set of non-overlapping cells, providing a framework for spatial indexing, aggregation, and analysis at any resolution.
IGEO7 is implemented in:
- DGGRID (C++) — the original reference implementation of ISEA7H and Z7
- DGGAL — supports IGEO7 via ISEA7H_Z7
- dggrid4py — Python wrapper for DGGRID, can take care of correct definitions
- pydggsapi — OGC API DGGS server that supports both dggrid4py and dggal
Core Properties
| Property | IGEO7 | H3 |
|---|---|---|
| Projection | ISEA (equal area) | Gnomonic |
| Cell shape | Hexagons + 12 pentagons | Hexagons + 12 pentagons |
| Aperture | Pure 7 | Custom toplevel, then 7 |
| Resolutions | 0–20 (21 levels) | 0–15 (16 levels) |
| Base cells | 12 | 122 |
| Index size | 64-bit integer | 64-bit integer |
| Area distortion | 0% | ±50% |
Next Steps
- Installation — Set up DGGRID and dggrid4py
- Quickstart — Your first IGEO7 cells in Python
- Resolution Table — All 21 resolution levels
- Z7 Indexing Concepts — How the index works