# [TECH] GPS (Global Positioning System)
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**GPS** is a satellite-based navigation system providing global positioning and timing to any receiver, accurate to ~3 m commercially and ~30 cm with augmentation, requiring corrections from both special and general relativity.
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## Overview
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The US DoD GPS constellation (24 satellites, first launch 1978, fully operational 1995) uses time-of-flight measurements from 4+ satellites to triangulate position. Each satellite carries an atomic clock; without relativistic corrections (SR: −7 μs/day; GR: +45 μs/day), position errors would accumulate at 10 km/day. GPS is used in navigation, precision agriculture, surveying, finance (timestamping), and now autonomous vehicles.
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## Key Actors
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- **Companies**: Rockwell International (GPS satellites), Trimble (1978), Garmin (1989), Qualcomm (chipsets), u-blox
- **Inventors**: Ivan Getting (1912–2003), Bradford Parkinson (1935–), Roger Easton (1921–2014)
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## Key Patents
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- Easton, R. US Patent 3,789,409 (1974) — navigation signal processing
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## Economic Value
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GPS contributes approximately **$1.4 trillion/year** to the US economy alone (RTI International for CGSIC, 2019). Global estimate: ~$2–3T/year. Precision agriculture GPS savings: $25B/year. Autonomous vehicles will add $500B+/year.
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## Notes
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RTI International *Economic Benefits of GPS* (2019). Global value extrapolated from US figure using GDP ratio. The system's construction cost (~$12B) is dwarfed by its economic return.
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# Parents
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* [TECH] Rocket & Space Launch⏎