Trip Odometer vs Track Distance

Some commonly asked questions regarding the Garmin GPSr Trip Computer
odometer include:
  • "Why is the Trip Computer odometer distance greater than my Track Log distance?"
  • "Why is the Trip Computer odometer distance less than my Track Log distance?"
  • "Which is correct?"

While these questions are easy to understand, the answers will require some explanation regarding Garmin GPSr recording functions.

Track Log

  • A Track Log consists of a series of track points (or bread crumbs) recorded by your GPSr.
  • Garmin GPSr allow the user to adjust how and when track points are recorded:

    Record Method

    • Distance (records new track points at a specified distance, regardless of time elapsed)
    • Time (records new track points at a specified frequency, regardless of distance traveled)
    • Auto (records new track points as needed, determined by direction of travel and velocity)

    Record Interval

    • Time (user selected time interval between recorded track points)
    • Distance (user selected distance interval between recorded track points)


Trip Computer

  • The Trip Computer records the total distance traveled and displays the information in the Trip Odometer data field.
  • The Trip Odometer distance will increase only when the GPSr position changes.
  • The Trip Odometer is updated at a fixed frequency of 1Hz, or once every second.
  • The Trip Odometer can be reset to zero at any time.


Example

  • Longer Track Log recordings will exhibit greater accumulated discrepancy than shorter Track Log recordings.
  • For clarity, only a very short section of track log is displayed in this example.

Every Track Log has a Start Point (A) and End point (B):
Odometer Issue AB.png

The GPSr will travel from Point (A) to Point (B):
Odometer Issue AB Track Direct.png
The actual path traveled between Point (A) and Point (B) requires navigating some obstacles:


Odometer Issue AB Track Curved.png


The Track Log records Track Points at the user specified interval:

Odometer Issue AB Track Points 4 Curved.png


The Track Log distance traveled is calculated between Track Points:

Odometer Issue AB Track Points 4 Curved Orange.png


The Trip Computer records Track Points at an interval of one per second (1Hz):

Odometer Issue AB Track Points 12 Curved.png


The Trip Computer distance traveled is calculated between Track Points:

Odometer Issue AB Track Record 12 Curved.png


The Trip Computer distance is greater than the Track Log distance:

Odometer Issue AB Track Record 4-12 Curved.png



Conclusion