Mini Altimeter

A barometric altimeter and GPS speedometer for hiking, skiing, trail running, cycling and flying. One screen, with nothing on it that is not a reading.

BOTH ALTITUDES, SIDE BY SIDE
Most altimeter apps make you choose between the pressure sensor and the satellite fix. This one shows both, always. They fail in different ways — the barometer drifts as the weather moves, GPS elevation wanders indoors and under trees — so seeing them together is what tells you whether to trust either. The difference between them is shown as a delta, and it is the most honest signal the app has: it is measured, not estimated.

WORKS WITH NO SIGNAL
There is no networking code in this app at all. Altitude is computed on the device from raw barometric pressure using the standard atmosphere, so the altimeter keeps working in a valley, inside a building, on a plane and in airplane mode.

LIVE ON YOUR LOCK SCREEN AND IN THE DYNAMIC ISLAND
Start a trip and the altimeter keeps running in the background. Your current altitude sits in the Dynamic Island, and the lock screen shows both altitudes, climb rate, ascent, descent and speed without unlocking the phone. End the trip and it all stops — background tracking is always something you chose.

WIDGETS
Home-screen widgets show your last altitude, pressure, ascent and speed, and say how long ago the reading was taken. They never pretend to be live.

APPLE WATCH
On a watch with a barometer it is a complete altimeter on your wrist, using the same calibration as your phone. On one without, it mirrors your iPhone's readings and says so.

TRIP RECORDING AND STATISTICS
Every trip is saved. Open it later for statistics shaped to what you were doing — pace and ascent for a hike, speed for a ride, exit and deployment altitude and freefall time for a jump, thermals, climb rates and glide ratio for a flight — with an altitude profile. The activity is recognised from the track itself, and on iPhones with Apple Intelligence the on-device model gives a second opinion. Trips store altitude, speed and pressure only, never where you were.

FOUR LOOKS
Glass — true black, lit numerals. Phosphor — a green terminal. Paper — ink on white. LCD — a grey-green segment display with a bar trace. Every one keeps every number in the same place.

CALIBRATION THAT MAKES SENSE
A pressure sensor measures changes to within about a metre, but it cannot know