Pro Altimeter for Watch 4+

Pro Altimeter for Watch is the newest Watch app from Hunter Research, developer of the popular outdoors app Theodolite. Pro Altimeter uses the high-fidelity barometric pressure sensor in the Apple Watch to measure and compute altitude. Although this is a Watch app, it has the same features, capabilities, and accuracy as the Pro Altimeter app for iPhone and iPad, just in a smaller form factor on your wrist!

Pro Altimeter has a dead simple interface. Barometric altitude and GPS altitude are displayed in large easy to read numbers, with available units of feet or meters, and realtime accuracy estimates from the hardware. At bottom are calibration and settings buttons. The display offers highly-readable color schemes of luminescent green on black, white on black, and midnight red on black.

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 numerous 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 that you trust.

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

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 "CAL" button. You should calibrate as frequently as practical -- for example, on a hike, calibrate whenever you pass a trail marker or elevation benchmark, or hourly. But at a minimum, calibrate at least every 6 hours or whenever weather changes in your area.

Pro Altimeter runs on all Apple Watch models running watchOS 8.3 or later.