Trip Odometer vs Tracklog Distance

 

Some commonly asked questions regarding the Garmin GPSr Trip Computer odometer include:

• "Why is the Trip Computer odometer distance greater than my Tracklog distance?"
• "Why is the Trip Computer odometer distance less than my Tracklog distance?"
• "Which is correct?"

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

Tracklog

• A Tracklog 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 Tracklog recordings will exhibit greater accumulated discrepancy than shorter Tracklog recordings.
• For clarity, only a very short section of Tracklog is displayed in this example.

Every Tracklog has a Start Point (A) and End point (B):

 

The GPSr will travel from Point (A) to Point (B):

 

The actual path traveled between Point (A) and Point (B) requires navigating some obstacles:

 

 

 

The Tracklog records Track Points at the user specified interval:

 

 

 

The Tracklog distance traveled between point (A) and point (B) is calculated between recorded Track Points:

 

 

 

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

 

 

 

The Trip Computer distance traveled between point (A) and point (B) is calculated between recorded Track Points:

 

 

 

The calculated Trip Computer distance is greater than the calculated Tracklog distance:

 

Conclusion

• Tracklog distance vs Trip Computer odometer will vary based on Track Record settings for each GPSr device.
• More Track Points generally translate into improved accuracy.
• Two options exist to achieve a Tracklog distance that closely resembles the Trip Computer odometer at Point (B):
  • Option One:
  • Set Track Record Method to Time
  • Set Track Record Interval to 00:00:01, or once per second (1Hz)
  • Clear Current Track and Reset Trip Computer Odometer at Point (A)
  • Option Two:
  • If your GPSr has a 'Trip Recording' option in the tracklog recording setup menu, do not choose 'Always'