Accuracy
From MB Wiki
Accuracy of Fitness and Recreation recording devices is extremely important to most people both during the activity and afterwards. There are many factors that can increase or decrease accuracy.
Elevation
Elevation from a typical GPS unit is less accurate than the horizontal position (latitude/longitude). Elevation can sometimes be off as much as 10 meters. Even at that accuracy it can be used as a good guide to understand where you are on a hill climb. While standing still the GPS elevation will often fluctuate exposing the inability to be confident of the absolute elevation.
Barometric altimeters use changes in air pressure to report a more accurate elevation reading than GPS units, however, changes in the weather can affect the readings dramatically. These types of devices also required calibration where the user inputs the known elevation so the device can report correct elevation readings. Calibration to a known elevation is rarely convenient.
Garmin GPS devices that use barometric altimeters to report elevation are the most accurate because they auto-calibrate themselves using the elevation reported from the GPS working with the barometer.
MotionBased Gravity uses the horizontal position reported from a GPS and cross-references the position to an elevation database that has been surveyed by professional organizations. The known position is accurate to as little at 3 meters which can be a good source of elevation.
Performance Ranking
MotionBased recommends the following methods in order of most accurate to least.
- GPS + Barometric altimeter with auto-calibration (Garmin units only)
- MotionBased Gravity correcting an accurate GPS device
- GPS-only altitude as provided by many popular Garmin fitness devices.
- barometric altimeter only device (accuracy is too dependent upon weather and user input).
