| GPS constellation | 31 satellites, maintained by US Space Force | ~5,000 | Industry estimate; [GPS.gov](https://www.gps.gov/) |
| Magnetometer/compass sensors | Enable the direction arrow to point at shelters | ~500 | Industry estimate |
| ARM architecture | The CPU instruction set running every Android device | ~5,000 | [Arm had 8,330 employees in 2025](https://www.macrotrends.net/stocks/charts/ARM/arm-holdings/number-of-employees); ~5,000 estimated over the architecture's 40-year history |
| TCP/IP, DNS, HTTP, TLS | The protocols that carry shelter data from server to phone | ~5,000 | Cumulative IETF/W3C contributors over decades |
| GeoJSON specification | The format the shelter data is published in (IETF RFC 7946) | ~50 | [RFC 7946 authors + WG](https://datatracker.ietf.org/doc/html/rfc7946) |
| EPSG / coordinate reference systems | The math behind UTM33N → WGS84 coordinate conversion | ~200 | [IOGP Geomatics Committee](https://epsg.org/) |
## Layer 2: Operating Systems & Runtimes (~23,800 people)
| Component | Role | Est. people | Source |
|---|---|---|---|
| Linux kernel | Foundation of Android | ~20,000 | [Linux Foundation: ~20,000+ unique contributors since 2005](https://www.linuxfoundation.org/blog/blog/2017-linux-kernel-report-highlights-developers-roles-accelerating-pace-change) |
| Android (AOSP) | Mobile OS, incl. ART runtime | ~2,000 | [ResearchGate study: ~1,563 contributors](https://www.researchgate.net/figure/Top-Companies-Contributing-to-Android-Projects_tbl3_236631958); likely higher now |
| OpenJDK | The Java runtime Kotlin compiles to | ~1,800 | [GitHub: ~1,779 contributors](https://github.com/openjdk/jdk) |
| Play Services Location | FusedLocationProvider for precise GPS | ~200 | Google internal; estimate |
| SQLite | The embedded database engine | **~4** | [sqlite.org/crew.html](https://sqlite.org/crew.html) — the most deployed database in the world, maintained by 3–4 people |
## Layer 6: Libraries — PWA (~1,750 people)
| Library | Role | Contributors | Source |
|---|---|---|---|
| Leaflet | Interactive web maps (created in Ukraine) | ~865 | [GitHub: Leaflet/Leaflet](https://github.com/Leaflet/Leaflet) |
| leaflet.offline | Offline tile caching | ~20 | Estimate based on GitHub |
| idb | IndexedDB wrapper for offline storage | ~30 | Estimate based on GitHub |
| vite-plugin-pwa | Service worker and Workbox integration | ~100 | Estimate based on GitHub |
| DSB | Created and maintains the public shelter registry | ~200 | [dsb.no](https://www.dsb.no/) |
| The shelter builders | Construction, engineering, civil defense planning since the Cold War | ~5,000 | Estimate based on ~556 shelters built 1950s–80s |
| Anthropic / Claude | Researchers, engineers, safety team | ~1,000 | [anthropic.com](https://www.anthropic.com/) |
| ML research lineage | Transformers, attention, RLHF, scaling laws — across academia & industry | ~5,000 | Estimate across all contributing institutions |
| Training data | The collective written output of humanity | incalculable | |