How do the ELEMNT, BOLT, and ROAM calculate elevation?
The ELEMNT, BOLT, and ROAM primarily calculates elevation data from a barometric altimeter which measures air pressure. While air pressure typically provides very accurate elevation measurements, it remains subject to factors like temperature and changing weather patterns. As with all barometric altimeters, environment changes can cause elevation readings to "drift," even when stationary or riding at on a level path.
To counter environmental elevation drift, barometric altimeters require regular adjustment. For this, the ELEMNT, BOLT, and ROAM uses GPS.
Why don’t the ELEMNT, BOLT, and ROAM primarily use GPS to calculate elevation?
GPS elevation is often unreliable due to GPS satellite positioning and coverage. In testing, we commonly found GPS elevation inaccuracies in hundreds of meters. Because of this, consistent and accurate elevation data is best achieved using GPS-adjusted barometric altimeter data.
How do the ELEMNT, BOLT, and ROAM use GPS to adjust elevation?
When a ride starts, the ELEMNT, BOLT, and ROAM calculates elevation using the barometric altimeter and compares it to the reported GPS elevation. If a discrepancy is found with the barometric altimeter elevation, the ELEMNT, BOLT, and ROAM adjusts using GPS data. Before this is done however, the ELEMNT, BOLT, and ROAM performs additional calculations to determine GPS elevation accuracy. If GPS elevation is deemed inaccurate, it is discarded and no adjustment is made. This prevents skewing elevation data with poor GPS data, but also means that certain situations may also prevent the ELEMNT, BOLT, and ROAM from correcting barometric altimeter drift with GPS.
What situations impact elevation data most?
Since the ELEMNT, BOLT, and ROAM uses GPS and barometric pressure to calculate elevation, these situations are likely to impact elevation readings:
- Large changes in temperature or humidity like stepping outdoors in the summer from an air-conditioned environment
- Riding in or near inclement weather like rain and snow
- Riding near large bodies of water
- Clogged or obstructed barometric altimeter ports
How do ELEMNT, BOLT, and ROAM elevation readings compare with other GPS bike computers?
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 the sole source of elevation data, despite the flaws in each of these outlined above.
On the rare occasion where barometric altimeter elevation drift cannot be corrected with GPS data, elevation accuracy may be skewed. However, these situations are unusual, occurring only when numerous environmental factors conspire with GPS signal issues. All devices calculating elevation with a barometric altimeter face these challenges.
By using multiple factors to calculate elevation, discrepancies can be resolved when the weather stabilizes or when accurate GPS data becomes available. This ensures the ELEMNT/BOLT/ROAM provides the most consistent and accurate elevation of any cycling computer currently available.
What can I do to improve elevation data?
Since the ELEMNT, BOLT, and ROAM needs good a GPS signal to achieve maximum accuracy, starting a ride after gaining full line of sight to the sky and acquiring a solid GPS connection ensures the best results.
Pairing a speed sensor like the Wahoo Blue SC or RPM Speed to your ELEMNT, BOLT, and ROAM can correct GPS inaccuracies and improve elevation and grade data when under tree/building cover or wherever GPS is unavailable.
You may also want to consider checking the barometric altimeter ports on your ELEMNT, BOLT, and ROAM and other solutions offered in the ELEMNT Data Accuracy article.