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):

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 Track Log records Track Points at the user specified interval:



The Track Log distance traveled is calculated between Track Points:



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



The Trip Computer distance traveled is calculated between Track Points:



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

Conclusion

• Track Log distance vs Trip Computer odometer will vary based on Track Record settings for each GPSr device.
• More Track Points generally translate into improved accuracy.
• To achieve a Track Log distance that closely resembles the Trip Computer odometer at Point (B):
  • 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)