Pro Altimeter - Barometric+GPS 4+

Manual/GPS/METAR Calibration

Craig Hunter

    • $0.99



Pro Altimeter uses the high-fidelity barometric pressure sensor in iOS devices to measure and compute altitude.

Pro Altimeter has a dead simple interface. Barometric altitude and GPS altitude are displayed in large easy to read numbers, showing units of both feet and meters, and giving realtime accuracy estimates from the hardware. At bottom are calibration and display mode buttons. The display offers a highly-readable daytime mode with black digits on an LCD-green background, and a reversed night mode that is easy on the eyes in dark conditions. That's it!

Proper calibration is necessary to measure altitude from barometric pressure (this is why a pilot "dials in" the cockpit altimeter before taking off). Pro Altimeter offers four different methods for calibration -- choose the easiest and most convenient:

1. Use GPS altitude. This method correlates the measured local barometric pressure with the altitude measured by GPS. This method can be used when your device has a clear line of sight to the sky and a reliable GPS fix with good accuracy.

2. Manually enter altitude. This method correlates the measured local barometric pressure with known altitude from landmarks, elevation benchmarks, trail markers, topo maps, land surveys, etc. Altitude can be entered in feet or meters.

3. Manually enter pressure. If you have a weather station, weather report, or METAR report with equivalent sea level pressure for a nearby location, this can be used to correlate local barometric pressure to altitude. Pressure can be entered with units of inches Hg, kPa, or mb.

4. Check local airports. With the tap of a button, Pro Altimeter will locate the five closest airports within 100 miles (160km) of your present location anywhere in the world, and pull in METAR data. From that list of five, pick the airport of your choice and Pro Altimeter will import pressure data for calibration.

Once calibrated, Pro Altimeter keeps track of the time since its last calibration. Because weather and local barometric pressure change over time, the app will warn you when 6 hours have elapsed since the last calibration by flashing the "CALIBRATE" button. You should calibrate as frequently as practical -- for example, on a hike, calibrate whenever you pass a trail marker or elevation benchmark. But at a minimum, calibrate at least every 6 hours or whenever weather changes in your area.

Pro Altimeter is intended for iOS devices with a built-in barometric pressure sensor (iPhone 6 and later, iPad Air 2 and later, iPad mini 4 and later, and iPad Pro). On older devices without a barometric pressure sensor, only GPS altitude and accuracy will be displayed.

If you have an Apple Watch, check out the new Pro Altimeter for Watch and get all this same functionality on your wrist!

What’s New

Version 1.1.1

Update to handle unannounced changes in the NWS AviationWeather API that supplies airport weather data for calibration.

Ratings and Reviews

4.0 out of 5
31 Ratings

31 Ratings

App_User_Beta ,

Pro Altimeter Update

This version of the App has effectively resolved an issue related to display on IPhone6. The app is easy to calibrate and read due to the larger text. Well worth the 0.99 cents.

Mettech32 ,

This is what I was looking for!

While trying to determine elevations for setting multiple very sensitive digital barometers at different levels indoors, I used a combination of USGS topo maps, a couple of pressure equations, and moving up and down hill with a barometer to record pressure changes to predict estimated altitudes where the stationary barometers are. Pretty much had to work it out inside-out and in reverse. Then I happened to see this altitude app available in the Theodolite app (never came across it when searching the App Store, though), and it’s exactly what I was needing. I took it to an open spot outside where an online high-res USGS topo map showed 1,261 feet elevation, entered that as the calibration, then quickly took my phone to the barometer locations. Based on the app elevation readings, the difference between the predicted pressure and the values calculated using this app’s numbers showed that the prediction was only 0.08 millibars off, or within about 5 feet elevation. It was kinda cool to see how closely the reverse-engineering turned out to be, but I’d much rather have skipped all that nonsense and found this app a lot sooner.

CC50 ,

Great calibration. How about some functionality?

Love the multiple methods of calibration and the accuracy it provides… but now this app needs some features to make it useful.
Climb and descent rate measured over time or between pre-determined altitudes for us climbers and skiers.
The ability to display change in altitude over time in both data table (exportable to spreadsheet) and graph/graphic form.
Altitude alarms to signal when a particular altitude has been reached.

Barometer: pressure change over time is a good indicator of weather trends. How about recording pressure at user selectable time intervals in the background and then displaying collected data in table form (exportable to spreadsheet) and graph/graphics forms?
Maybe display airport data on a map so user can see surrounding pressure readings and get a picture of pressure trends in area?

App is a good start from an accuracy, calibration point of view. Now add some useful functionality.

App Privacy

The developer, Craig Hunter, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy.

Data Not Collected

The developer does not collect any data from this app.

Privacy practices may vary, for example, based on the features you use or your age. Learn More


  • Family Sharing

    Up to six family members can use this app with Family Sharing enabled.

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