Name: Density Altitude and ISA Deviation Calculator
Rating: 5 (1 reviews)
Author: Freitag

WARNING: The app is intended only as an in-flight aid and should not be used as a primary information source. If the app contains a barometric altimeter, it will not function in a pressurized aircraft and should not be used in a pressurized aircraft.

Density Altitude and ISA Deviation Calculator is a Connect IQ Aviation app for pilots who want a fast, practical way to assess atmospheric conditions directly on their Garmin watch.

The app calculates density altitude, pressure altitude, and ISA deviation from pilot-entered values such as field elevation, outside air temperature, and QNH. Temperature is displayed in the unit configured on the watch. The QNH unit can be selected in the app settings - hPa/mbar, inHg, or mmHg - because Connect IQ does not give apps access to the watch's own pressure unit setting.

On startup, the calculator can initialize field elevation from the watch altimeter, estimate QNH from the built-in barometer, and read outside air temperature from the connected weather service. These values provide a convenient starting point and can be adjusted manually before flight.

It is designed for quick use before flight, during planning, or as a cross-check at the airfield - for general aviation pilots, flight instructors, and aviation enthusiasts.

Key features:
- Density altitude, pressure altitude, and ISA deviation
- Selectable QNH unit: Auto, hPa/mbar, inHg, or mmHg
- Elevation, QNH, and OAT prefilled from altimeter, barometer, and weather service
- Simple pilot-focused input workflow
- Button and touchscreen operation

=====================================
User Guide

Density Altitude and ISA Deviation Calculator calculates Density Altitude (DA) and Pressure Altitude (PA) from QNH, outside air temperature, and field elevation. It is for reference only - always use POH/AFM and current METAR/ATIS for flight planning.

Initialization on startup
On startup, field elevation is read from the watch altimeter, QNH is estimated from the barometer, and OAT is loaded from the connected weather service. These values do not update continuously - adjust them manually to current METAR/ATIS before use.

Display
The large center value shows Density Altitude. The active input field shows its current step size next to its name, for example QNH +-1. The color indicates ISA deviation: warm color = above ISA, cool color = below ISA, white = ISA standard. The two dots at the bottom of the screen indicate the current page.

Button controls
Press SELECT to switch between QNH, OAT, and ELEV. Use UP and DOWN to change the active value. Long press UP (MENU) to open the settings. Press BACK to exit.

Touch controls
Tap - or + to decrease or increase the active value. Tap and hold - or + for larger steps. Tap an input field to switch to the next one; tap and hold an input field to toggle between fine and coarse steps.

Settings
Long press UP (the standard menu gesture), swipe left, or tap the dots at the bottom of the screen to open the settings menu. Under QNH Unit you can select Auto, hPa/mbar, inHg, or mmHg. Coarse Steps switches between fine and coarse step sizes. Auto derives the unit from the elevation unit configured on the watch (meters = hPa, feet = inHg). Please note that the pressure unit set under the watch's aviation settings is not available to Connect IQ apps, so it has to be selected here separately. Both settings are saved and remain active after restarting the app. Swipe right or press BACK to return.

Step sizes (fine / coarse)
QNH: 1 hPa, 0.01 inHg, or 1 mmHg / 5 hPa, 0.05 inHg, or 5 mmHg
OAT: 1 deg / 5 deg
ELEV: 10 ft / 100 ft