Why am I seeing differences in elevation in my ride data?

How does the ELEMNT calculate elevation?

The main source of elevation data reported by the ELEMNT is from a barometric altimeter, which uses air pressure to measure elevation. In most cases, air pressure is a very accurate measure of elevation, but can be affected by local environmental factors such as temperature and wind. As is the case with all barometric altimeters, when the environment is changing the elevation may change, or drift, even if you are stationary or riding at a constant elevation.

In order to adjust for elevation drift due to environmental factors, barometric altimeters require regular adjusting to ensure accurate elevation. The ELEMNT uses elevation from GPS to help perform these adjustments.

Why doesn’t the ELEMNT use GPS primarily to calculate elevation?

The main reason is that elevation from GPS can be extremely unreliable due to positioning of the GPS satellites. We have found that elevation from GPS can be inaccurate for extended periods of time, and can result in recorded elevations that are hundreds of meters off from actual elevations. In our opinion, the best way to get consistent and accurate data is to use the barometric altimeter calculate elevation and adjust for elevation drift using GPS.

How does the ELEMNT use GPS to adjust elevation?

During the ride, the ELEMNT will calculate elevation from air pressure using the barometric altimeter and compare to the GPS elevation. If a discrepancy is found with the altimeter elevation, the ELEMNT will adjust using GPS elevation. Before this is done, the ELEMNT first performs advanced calculations to determine if the GPS elevation is accurate. If GPS elevation is deemed inaccurate it is not used, and no adjustment is made. Although this prevents polluting the altimeter elevation with poor elevation from GPS, it also means that at certain times ELEMNT cannot use GPS elevation to remove drift.

How does the ELEMNT elevation readings compare to other GPS computers?

We believe that using altimeter elevation and correcting drift with GPS data is the best way to provide consistent and accurate data. Some computers use either altimeter data or GPS data as their only way of recording elevation.  These methods encounter the same issues outlined above and although mostly accurate can be extremely inaccurate for periods of time.

In rare occasions, the ELEMNT may record what seems like inaccurate data due to elevation drift and the inability to get accurate GPS elevation data. These occurrences are caused by environmental factors and will be seen on any device that uses a barometric altimeter for elevation. For the ELEMNT, the data inaccuracies will be resolved when the environment returns to normal or an accurate GPS elevation is obtained.