The Barometer

[F27]

I keep reading the press erroneously reporting that the Band's new Barometer is there to track elevation.

But that's not what a Barometer does! what they are talking about is an Altimeter. A Barometer predicts the weather. So with that said, is the new Band going to predict local weather? what is it doing in there? It's slightly confusing.

I was hoping this would finally be a replacement for an A,B,C watch but I guess that's not the case as it doesn't have an Altimeter.

 

[Tumultus]

Aren't barometers and pressure altimeters essentially the same thing?

 

[Philipp H]

From the Microsoft site:
"Sensors
[...]Barometer
"
so yes, it has a Barometer.
But a Barometer can (as in planes) also be used as an Altimeter.

 

[F27]

Then is must be some sort of combined Alti-Baro chip, they really should have called it an Altimeter to be clearer.

You can be the same height above sea level and have different levels of atmospheric pressure which is how a Barometer works, actually the levels change every day and it's not indicator of altitude. Like when you see high and low pressure on weather reports.

This is why they call them A,B,C watches because an Altimeter and Barometer are not the same thing. They work in a similar way but are two separate entities.

 

[Tumultus]

From Wikipedia:

A barometer is a scientific instrument used in meteorology to measure atmospheric pressure. Pressure tendency can forecast short term changes in the weather. Numerous measurements of air pressure are used within surface weather analysis to help find surface troughs, high pressure systems and frontal boundaries.

Barometers and pressure altimeters (the most basic and common type of altimeter) are essentially the same instrument, but used for different purposes. An altimeter is intended to be transported from place to place matching the atmospheric pressure to the corresponding altitude, while a barometer is kept stationary and measures subtle pressure changes caused by weather. The main exception to this is ships at sea, which can use a barometer because their elevation does not change. Due to the presence of weather systems, aircraft altimeters may need to be adjusted as they fly between regions of varying normalized atmospheric pressure.

I do believe you that those 2 aren't the same thing, however, it seems like you can use a barometer as altimeter (as long as you don't expect precision).

 

[F27]

As long as it measures elevation then that's what I'm after. There is not real need for weather predication if it's linked to the weather reports on your phone but it would be cool to have dynamic weather monitoring on your wrist.

 

[Tumultus]

I am no expert, so, don't take my word for it: From my (limited) technical understanding, it should be possible to use a barometer, combined with GPS / location data and some software trickery to use it as an altimeter. It won't be very precise and accurate but for most people, it probably would be good enough.

Microsoft says this on the Band 2 page:

Barometer
Track your fitness with more precision with a built-in barometer that measures elevation changes while running, biking, or just climbing stairs.

 

[Nate Silver]

Probably a more specific term would have been a 'barometric-altimeter'. Theoretically, they are more accurate than elevation measured via GPS. In practice, results are rather mixed. I think it depends on how they implemented it. My Garmin Fenix 3 has a barometer/altimeter feature, and for the most part is reasonably accurate, though occasionally required calibration, and I don't know how (or if) MS is going to handle calibration. The rub is that (obviously), these sensors are also affected by weather related pressure changes. Some manufacturers utilize complex logarithms to help it determine what is true elevation change vs weather. Most of the time they get it reasonably right.

 

[DroidUser42]

Aren't barometers and pressure altimeters essentially the same thing?

Yes. The difference is how you interpret the results. Airplanes have to adjust their altimeters to give correct reading based on the nearby barometer reading.

This gets to be a real challenge when dealing with a device that moves around - is the change due to elevation, weather, or building HVAC? Users of other fitness devices have reported erroneous results.