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Confidence and Accuracy

This guide explains how location confidence and accuracy are handled in the Tracker GraphQL system.

Confidence Values​

The confidence field in location reports and location history records indicates the reliability of the location data.

Current Scale (1-3)​

As of April 2025, the confidence field uses a simple scale from 1 to 3:

ValueDescription
1Low confidence
2Medium confidence
3High confidence

This scale directly reflects the confidence values provided by the FindMy API.

Previous Scale (Percentage)​

Prior to April 2025, the confidence field used a percentage-based scale (0-100%). This has been replaced with the simpler 1-3 scale to better align with the underlying API.

Filtering Based on Confidence​

By default, the system filters location history records to only include medium to high confidence reports (confidence >= 2). This ensures that only reliable location data is used for tracking and analysis.

This filtering is applied in several places:

  • The continuous aggregates for location history
  • The geofence processing function
  • Various frontend components

Horizontal Accuracy​

The horizontalAccuracy field was added in April 2025 to provide more detailed information about the precision of location data.

Understanding Horizontal Accuracy​

Horizontal accuracy represents the accuracy radius in meters. It indicates how precise the reported coordinates are:

  • Lower values (e.g., 10-30 meters) indicate more precise location data
  • Higher values (e.g., 100+ meters) indicate less precise location data

Usage in the UI​

The horizontal accuracy is displayed in the UI alongside the confidence value to give users a more complete picture of the reliability of location data:

  • In the tracker map view, the accuracy is shown in meters for each location point
  • In the location timeline, the accuracy is displayed for each location entry

Technical Implementation​

The horizontal_accuracy field is:

  • Stored as a Float in the database
  • Propagated through the materialized views for location history
  • Available in all GraphQL queries that return location history data

Example GraphQL Query​

This query retrieves location history with both confidence and horizontal accuracy information:

query {
  locationHistoryByTimeRange(
    trackerId: "123"
    startTime: "2025-04-21T00:00:00Z"
    endTime: "2025-04-28T23:59:59Z"
  ) {
    id
    timestamp
    location {
      latitude
      longitude
    }
    nearestCity
    confidence
    horizontalAccuracy
  }
}

Best Practices​

  • For critical applications, consider filtering out locations with low confidence (confidence < 2)
  • Use the horizontalAccuracy field to further refine location data quality assessment
  • When displaying location data on maps, consider visualizing the accuracy radius to give users a sense of the precision