ZAirMeter

Make use of your built-in barometer to measure relative height, wherever you go!

ZAirMeter is an app developed for users to quickly measure relative altitude.

Most barometers are sensitive enough to accurately record height changes of +- 0.4m and below.

Instructions:

1. Hold the device and click the button to take the first measurement.
2. Move to a different altitude (take elevator, stairway), then hold the device steady and tap again to take the second measurement.
3. The height (altitude difference) will be displayed.

Note: A longer acquisition time may provide more accurate measurement:
This can be done by pressing and holding the button for a longer time (over 4 seconds).

How does this work?

Higher altitude makes the air pressure decrease.
The app measures relative altitude (pressure differences) with measurements done within minutes using a generic pressure to altitude conversion formula.

Why measurements must be done within minutes?
Because the air pressure changes with weather, so measurements done in minutes are less affected from changing weather. Remember that 1mb variation corresponds to around 8.3m.

Why not showing the sea level altitude and the difference?
Because the sea level pressure altitude changes with the weather: to make a plane safely land, the local and present equivalent airport sea level pressure must be beamed to the landing plane. For the phone app, it would require using internet (roaming) access to airport's METAR data. For more reading on the subject, search on QNH altitude. (ever thought about the tides effect on the sea level pressure?)

Quiz: Would a phone placed within an inflated bladder bag be able to measure the weight of an object?

Tags: Altimeter, pressure sensor, relative height measurement, barometer, barometric.