Introduction
"My GPS says I'm in the middle of the road, but I'm actually on the sidewalk!" Sound familiar? GNSS accuracy isn't one-size-fits-all. Depending on your equipment and techniques, you can get anything from 5-meter to 5-millimeter accuracy.
Accuracy Levels: The Big Picture
| Accuracy | Typical Use | Technology | Cost |
|---|---|---|---|
| 5–10 m | Smartphones, car navigation | Standard GPS | Free |
| 1–3 m | Fitness watches, drones | Multi-GNSS + SBAS | $50–$500 |
| 10–50 cm | Precision agriculture | DGNSS | $1,000–$5,000 |
| 1–5 cm | Surveying, construction | RTK | $5,000–$20,000 |
| <1 cm | Scientific research | Advanced RTK/PPK | $20,000+ |
Why Smartphone Accuracy Is Limited
- Single-frequency (mostly), can't correct ionosphere
- Small antenna, can't reject multipath
- Power constraints, continuous high-precision drains battery
Improvements Coming: Dual-frequency phones (iPhone 14+, Pixel 6+) now achieve 30–50 cm in ideal conditions.
The Accuracy Triangle
Three factors determine final accuracy:
1. Satellite Geometry (DOP)
- Are satellites spread out or clustered?
- Better spread = better accuracy
2. Error Sources
- Atmospheric delays
- Multipath
- Clock and orbit errors
3. Receiver Quality
- Number of frequencies
- Antenna quality
- Processing algorithms
Vital Points
- Accuracy ranges from meters to millimeters depending on technology
- Smartphones are improving but still limited by hardware
- Error sources determine theoretical limits
- Choose your accuracy based on needs and budget