Learning Lesson - Understanding Accuracy and Precision with GPS (Garmin Map60cx)

Geospatial Technology September 27, 2011 Print Friendly and PDF

General GPS Lesson – Exploring the Accuracy of Recreational Grade GPS Units

Instructional Information
GPS UNIT Level Menus/Pages
Garmin GPSmap 60cx Basic Find, Map, Compass

Summary: GPS accuracy and precision is always a topic of interest. This exercise is designed to demonstrate the level of accuracy and precision you can expect with recreational grade units.

Discussion: A general assumption with GPS units is that they can lead you to the exact location of a place, or that you can mark something with precise location coordinates. It’s important to understand the limitations of recreational grade GPS units. Recreational grade GPS units have a traditional accuracy of between 2-5 meters in general.

Instructor Set Up Select a location outside and place a marker such as a flag or other visual item at the location. Record the coordinate location with your unit.

Exercise

Garmin Map60cx image

 

Creating a Waypoint

 

  1. Turn your GPS Unit on.
  2. Allow unit to acquire current position troubleshooting: If unit does not report position, go to the Map page and press menu. Make sure the unit is using active GPS and not in simulation mode.
  3. Create a new waypoint.
    1. Go to the Map page.
    2. Select the Mark Button. A named waypoint will come up by default. That’s okay; we are going to rename it.
    3. Use the cursor to move to the top field.
    4. Create a name for your point.
    5. Use the cursor to move to the Location field.
    6. Type in the location the instructor has given you.
    7. Select OK to confirm the coordinates.
  4. Return to the Map Page.
  5. Press the FIND button.
  6. Highlight Waypoints.
  7. Press the ENTR button.
  8. Press QUIT to see a list of all symbols.
  9. Use your cursor to find the waypoint you edited above.
  10. Select “Go To” on the bottom menu to begin to navigation.
  11. You are now on the Map Page.
  12. Begin walking until your unit indicates you are at the location.
  13. Place a marker at your spot.

Observations

  1. How many markers were at the exact location of the mark of your instructor? Accuracy
  2. Were the marks clustered or spread out? Precision

Learning Points Accuracy is the degree in which you were correct. If all of your marks were in the proximity around your instructor's, then you have a high level of accuracy.

Precision is the ability to reproduce findings over and over. If all your marks were in the same spot and not spread all around your instructor's, then you have a high level of precision.

 

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This work is supported by the USDA National Institute of Food and Agriculture, New Technologies for Ag Extension project.