Stefan Mikes
Well-Known Member
- Region
- Europe
- City
- Mazovia, Poland
To be able to determine the elevation gain of our ride, we need an altimeter. These are the altimeters that we can use for e-biking:
The Aviation Altitude Measurements
An aircraft that is cruising at a high altitude (such as 36,000 to 41,000 ft) has the reference pressure of 1 atm, or 1013.25 hPa set. At high altitudes, the ambient pressure is only depending on the altitude. Is the actual altitude of the aircraft 40,000 or 40,100 ft is unimportant. All aircraft have their reference pressure set to 1013.25 hPa or 29.92 in Hg. Therefore, the vertical separation between different airplanes can be easily determined.
Once the airplane is on the descent and approach towards the airport, the Air Traffic Control always informs airline pilots about the updated QNH, which is the actual pressure at the airport runway. The barometric altimeter of the aircraft is updated with the current reference pressure. Therefore, the barometric altimeter knows exactly how high the aircraft is above the runway. To make the altitude measurement top accurate, the radio altimeter kicks in at a very low altitude. GPS is the third source of information ('Terrain! Pull up! Pull up!')
The Cycling Elevation Gain Measurement
In almost all situations, the current air pressure readout is taken as the reference by the e-bike, smartphone or GPS bike computer and set as a constant value when we push the START button. Now, as we climb, the ambient pressure will drop with the altitude, which is measured as the elevation gain. However, the ambient pressure at the altitudes we ride varies with the weather. If the outside pressure drops because of the weather, the barometric altimeter will record big elevation gain; or, the pressure might increase (weather improving), recording a low elevation gain.
The barometric altimeter used on a bike will always be wrong, especially on a long ride with variable weather.
How Can We Solve It Now?
Upload your ride to Strava. In the website (computer), you will see this:
Then, click
Strava will correct the elevation gain to the ride map. Example:
As measured by a barometric altimeter...
As measured on the map.
In the smartphone Strava app, click the "hamburger" icon next to your ride, then 'Adjust elevation'.
How Could It Be Fixed In The Future
Any GPS bike computer has access to the maps. A Garmin Edge or Wahoo ELEMNT know everything about your route, or where and at what altitude you currently are. For instance, you can see the map of all upcoming climbs on the route! Why not to do the elevation calculation based on the map? Could be done in the future but it looks neither Garmin nor Wahoo are really interested... Your life doesn't depend on that! (Several years ago the GPS bike computer maps were 2D, so all the development went into the barometric altimeter).
After reading the above, I hope none of you will need to ask again why the Elevation Gain data you got from your ride were wrong...![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
- E-bike barometric altimeter (available on some advanced e-bikes)
- Smartphone altimeter (will work with ride trackers such as Strava, Komoot, RideWithGPS, or a specific application of your e-bike)
- Bike GPS computer (Garmin, Wahoo, Hammerhead...)
The Aviation Altitude Measurements
An aircraft that is cruising at a high altitude (such as 36,000 to 41,000 ft) has the reference pressure of 1 atm, or 1013.25 hPa set. At high altitudes, the ambient pressure is only depending on the altitude. Is the actual altitude of the aircraft 40,000 or 40,100 ft is unimportant. All aircraft have their reference pressure set to 1013.25 hPa or 29.92 in Hg. Therefore, the vertical separation between different airplanes can be easily determined.
Once the airplane is on the descent and approach towards the airport, the Air Traffic Control always informs airline pilots about the updated QNH, which is the actual pressure at the airport runway. The barometric altimeter of the aircraft is updated with the current reference pressure. Therefore, the barometric altimeter knows exactly how high the aircraft is above the runway. To make the altitude measurement top accurate, the radio altimeter kicks in at a very low altitude. GPS is the third source of information ('Terrain! Pull up! Pull up!')
The Cycling Elevation Gain Measurement
In almost all situations, the current air pressure readout is taken as the reference by the e-bike, smartphone or GPS bike computer and set as a constant value when we push the START button. Now, as we climb, the ambient pressure will drop with the altitude, which is measured as the elevation gain. However, the ambient pressure at the altitudes we ride varies with the weather. If the outside pressure drops because of the weather, the barometric altimeter will record big elevation gain; or, the pressure might increase (weather improving), recording a low elevation gain.
The barometric altimeter used on a bike will always be wrong, especially on a long ride with variable weather.
How Can We Solve It Now?
Upload your ride to Strava. In the website (computer), you will see this:
Then, click
Strava will correct the elevation gain to the ride map. Example:
As measured by a barometric altimeter...
As measured on the map.
In the smartphone Strava app, click the "hamburger" icon next to your ride, then 'Adjust elevation'.
How Could It Be Fixed In The Future
Any GPS bike computer has access to the maps. A Garmin Edge or Wahoo ELEMNT know everything about your route, or where and at what altitude you currently are. For instance, you can see the map of all upcoming climbs on the route! Why not to do the elevation calculation based on the map? Could be done in the future but it looks neither Garmin nor Wahoo are really interested... Your life doesn't depend on that! (Several years ago the GPS bike computer maps were 2D, so all the development went into the barometric altimeter).
After reading the above, I hope none of you will need to ask again why the Elevation Gain data you got from your ride were wrong...
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