Sensitive Altimeter

"For some reason, I feel a powerful compulsion to own any device whose name ends in -ometer" - XKCD #2060

This Android application measures air pressure using internal barometric sensor in the portable device and displays it on a three-pointer altitude indicator similar to the altimeter gauge in aircraft. Digital indication is also available.

The long hand shows hundreds, the short hand shows thousands, and the thin line with triangle tip shows tens of thousands of the selected altitude unit (meters/feet). Below the "warning altitude" (default 10000), a striped segment is visible.

Barometric altimeters will NOT work inside the pressurized cabin of an airliner.

These screenshots were taken in Salt Lake City airport. Altimeter setting: 30.25 inches of mercury.

Installation

App page on Google Play

Altimeter setting

Barometric altimeters compute the altitude based on the ratio between a barometer reading and pressure setting from a ground weather station. This setting is the station's barometer reading corrected to mean sea level, accurate only in the vicinity of the reporting station [1].

Manual adjustment

Clicking the pressure counter will open a dialog window where the reference pressure can be entered.

With "Classic" dial indicator type, reference pressure can be adjusted manually by dragging a finger around the dial center.

For manual adjustment, altimeter setting can be received from an airport's ATIS using an airband receiver.

Automatic adjustment

When Internet connection is available, the app can use altimeter setting (QNH) from METAR data from the nearest aviation weather station on the NOAA site [2]. In this case, the indicated altitude will be above mean sea level (MSL). The NOAA weather site has observation data from all aviation weather stations in the world.

Type ICAO location code (4 characters) in the text field and press "Update". Examples of ICAO codes:

`KLAX`	Los Angeles International Airport
`EDDF`	Frankfurt am Main (Germany)
`UUEE`	Sheremetyevo (Moscow, Russia)

Weather Stations

If the Weather Stations application is installed, clicking "Nearest" in the station selection dialog opens the nearest station list provided by that app.

Privacy policy

This application makes network connections only to NOAA sites. It does not contain ads, trackers, or any other types of malware. Device location data is used to sort the weather station list by distance. The author is not responsible for data collection by Google services and other applications.

Options

On Galaxy S5, press and hold Multitasking key to open the app menu.

Reference pressure can be specified in hPa, mmHg, inHg. Altitude unit (meters/feet) and warning altitude can be configured in "Indicator" options menu.

How it works

Altitude is calculated using the ICAO standard atmosphere model [3]:

\[ \begin{equation} h' = H' \left(1 - \left( \frac{p}{p_0} \right) ^ \frac{1}{n' + 1} \right), \\ \end{equation} \] \[ \begin{equation} p_0 = 1013.25 hPa, \\ \end{equation} \] \[ \begin{equation} H' = 44330.77 m, \\ \end{equation} \] \[ \begin{equation} n' + 1 = 5.25593 \end{equation} \]

References

Federal Aviation Administration, 2016 Pilot's Handbook of Aeronautical Knowledge
ADDS METARs - Aviation Weather Center
F. Herbert "The ICAO-standard atmosphere" - Volume 4a of Landolt-Börnstein - Group V Geophysics, pp 134-138

Video

Samsung Galaxy s3 barometer test in a bell jar - YouTube video by Simon Spiers