Symptom

A customer compares:

• the real mileage recorded by a GPS tracking system,
• and the distance returned by PTV xRoute for the same trip.

Example:

• GPS/tracking system distance: ~138 km
• xRoute calculated distance: ~218 km

The route is calculated using:

• xRoute
• more than 100 waypoints extracted from GPS positions
• toll calculation use cases

Despite the high number of waypoints, the reconstructed route differs significantly from the actual driven path.

The issue is typically observed when trying to:

• estimate toll kilometers,
• replay historical trips,
• reconstruct real vehicle trajectories from GPS traces.

Cause

This behavior is expected and is related to the fundamental difference between:

• route calculation  (xRoute)
• and map matching (xMatch).

xRoute behavior

xRoute does not reproduce the exact driven trajectory.

Instead, it:

• calculates a legally routable path,
• optimizes according to routing rules,
• and may choose roads different from the ones actually driven.

Even with many waypoints:

• xRoute is not designed to strictly follow raw GPS traces,
• intermediate GPS points are treated as routing waypoints, not as a continuous trajectory.

This can lead to:

• route deviations,
• longer distances,
• different toll sections,
• and inconsistencies compared to telematics systems.

Why the difference can become large

Several factors can increase the gap between GPS mileage and reconstructed routing distance:

• sparse GPS sampling,
• inaccurate GPS positions,
• missing intermediate points,
• off-road snapping behavior,
• routing optimization decisions,
• toll-preferred or legally valid alternative roads.

Important distinction

Resolution

For toll analysis and reconstruction of real vehicle trajectories,  use xMatch instead of xRoute.

Recommended approach

Step 1 — Use xMatch (Map Matching)

xMatch is specifically designed to:

• match GPS traces to the road network,
• reconstruct the actual driven path,
• improve toll distance estimation.

Unlike xRoute, xMatch does not recalculate an optimal route.

Step 2 — Ensure sufficient GPS density

Map matching quality strongly depends on GPS trace quality.

Recommendations:

• provide dense GPS traces,
• reduce the distance between recorded positions,
• reduce the recording time interval,
• avoid large gaps between points.

Sparse GPS data may cause:

• matching gaps,
• incorrect path reconstruction,
• incomplete toll calculations.

Step 3 — Handle possible gaps

If GPS points are too far apart:

• xMatch may not reconstruct a continuous path,
• additional routing between matched segments may be required.

This gap-filling step is not automatically handled by the standard xMatch workflow.

Reference

xMatch / Map Matching Use Case