What is Map Matching and Why Does It Matter?

Definition
Map matching snaps raw GPS coordinates to actual road segments. GPS reports you are at 37.7749, -122.4194. Map matching determines you are on Market Street heading east. It converts noisy coordinate sequences into clean road-network paths.
Why Raw GPS Is Not Enough
GPS accuracy is 5-15 meters in ideal conditions, worse in urban canyons. A point 10 meters from the road appears to be in a building or on the wrong street. Sequential points zigzag across road boundaries. You cannot compute accurate distance traveled or determine which road segment the vehicle used.
Map matching disambiguates. When GPS shows you between two parallel roads, map matching uses context: previous points, road connectivity, legal turns, speed limits. It infers the most likely actual path.
Core Applications
Navigation: Show vehicle on the correct road. Display upcoming turn instructions. Calculate accurate ETA based on road type and traffic.
Billing: Ride-sharing calculates fare from road distance, not straight-line GPS distance. A winding mountain road should cost more than a direct highway.
Analytics: Traffic analysis needs to know which roads are congested. Raw GPS points scattered around intersections are useless. Matched paths show actual traffic flow.
Fleet management: Did the driver take the assigned route? Geofence violations based on road segments, not circular radius.
💡 Key Insight: Map matching transforms GPS noise into road network facts. Without it, you have approximate positions. With it, you have actual paths, accurate distances, and road-level context for routing, billing, and analytics.

💡 Key Takeaways

✓GPS accuracy is 5-15 meters; points appear on wrong roads or in buildings

✓Map matching snaps coordinates to road segments using context and connectivity

✓Enables accurate distance calculation, ETA, billing, and traffic analysis

✓Disambiguates between parallel roads using previous points and road network

✓Converts noisy point sequences into clean road-network paths

📌 Interview Tips

1Explain the parallel road problem: GPS shows point between two streets, map matching uses path history to determine which

2For billing, emphasize that road distance matters: winding route should cost more than straight line

3Navigation needs matched path for turn-by-turn: raw GPS cannot determine upcoming intersection

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