What is a barometer?
A barometer is a device that measures atmospheric pressure. Because this pressure changes with distance above or below sea level, it can also be used to measure altitude.
The barometric altimeter in wearables is typically used to determine changes in elevation as well as changes to the pressure caused by weather patterns. There are a few factors that influence the barometric altimeter readings including rapid changes in weather, extended periods of time in a fixed location, moving to and from climate controlled or pressurised environments, debris blocking the sensor, clothing covering the sensor.
What type of barometers are used in wearables?
The latest wearable technology has built in microelectromechanical system (MEMS)-based barometers unlocking a wide range of tracking capabilities beyond just pressure and altitude measurement. A MEMS pressure sensor consists of a thin plate of silicon mounted as the lid of a chamber containing gas at a reference pressure (or a vacuum). The plate's top surface is exposed to atmospheric pressure via an opening or port in the sensor package. The difference in pressure will flex the plate, and create a mechanical strain that generates an electrical signal - this gives information about the pressure and ultimately, altitude.
As mentioned earlier, rapid changes in weather including an ill-timed gust of wind can cause a temporary drop in air pressure at the sensor just as it takes a measurement. This ‘noise' can cause what looks like an abrupt change, however such a change can be validated with the accelerometer reading. If there is no corresponding acceleration, then the altitude ‘jump' will be easily disregarded.
Why do wearables have barometers?
While accelerometers inside wearables feature a key motion sensor to determine the speed and acceleration of the user, they are limited in their ability to provide an accurate estimate of the vertical motion, which is essential for accurately determining certain parameters such as calories burned whilst climbing a high. The addition of a precise atmospheric pressure sensor can greatly improve accuracy in measuring this vertical movement and also helps in the validation of information from other sensors.
For example, whilst accelerometers can, in the majority of cases, capture your steps taken, distance travelled and calories expended, the measurement of vertical motion is a challenge for such sensors. Walking up stairs is sufficiently different to be picked up by the accelerometer through your acceleration profile, however walking along an incline is very difficult to distinguish from walking on level ground based only on acceleration. However, the effort exerted is substantially different.
Hence, the barometer captures this altitude shift calculated from how the atmospheric pressure changes as you walk uphill. In fact, some of the early generation wearables can be up to 30% off in their estimates of calories burned due to this omission of altitude. By integrating recordings from the barometer sensor into their algorithms, wearables can be far more precise.
Barometer data for precise locations in buildings...
Barometer data is able to help where our destination is on a specific floor of a building. For example, if you were in a large shopping mall a barometer would be able to let you know which floor you were on and give you precise instructions on how to get to your favourite store. Integrating our barometer with our maps would be able to give us this precise information. As we continue to see new developments in wearable technology, more opportunities are emerging for apps to be built using the data tracked.
Through the Terra API, we provide connections to a range of different devices that have built-in barometers.
Below is a list of the wearables that contain barometers today:
- Garmin Fenix series, Venu series (excluding sq, sq music), Approach series, Vivoactive, Forerunner series (excluding 45, 45 plus, 55, 245, 245 plus), Instinct series, Enduro, Descent series, Mk2 series, Epix, Tactix series, D2 series, Vivomove series, Approach series, Marq series, Quatix series
- Fitbit Versa series, Charge series, Inspire 2, Sense, Luxe, Ace 3,
- Apple Watch all series from Apple Watch series 3
- Polar Grit X Pro, Grit X, Vantage series (excluding Vantage M & M2),
- Withings ScanWatch series,
- Samsung Galaxy Watch 4, Galaxy Watch 3, Galaxy Watch Active 2
- Suunto 9 range, 7 range, Ambit3, Core range, Traverse
- Wahoo Elemnt Rival Multisport GPS watch
- Coros Vertix 2, Vertix, Apex, Pace 2
