Density Altitude and ISA Deviation Calculator

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. It uses the unit settings configured on the watch, so values are entered and displayed in the units already familiar to the user. On startup, the calculator can initialize field elevation from the watch GPS, 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. The calculator helps pilots understand how current conditions differ from the International Standard Atmosphere and how these deviations may affect aircraft performance. It is designed for quick use before flight, during planning, or as a cross-check at the airfield, useful for general aviation pilots, flight instructors, and aviation enthusiasts. Key features: - Density altitude calculation - Pressure altitude calculation - ISA temperature comparison - QNH-based atmospheric assessment - Automatic field elevation from watch GPS on startup - Automatic QNH estimation from the built-in barometer on startup - Automatic OAT from connected weather service on startup - Simple pilot-focused input workflow - Optimized for Garmin aviation and outdoor watches - Uses the watch's configured units for QNH and temperature - 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. Initiation oder startup On startup, field elevation is read from GPS, QNH is estimated from the barometer, and OAT is loaded from the connected weather service. Display The large center value shows Density Altitude. The color indicates ISA deviation: warm color = above ISA, cool color = below ISA, white = ISA standard. Button controls Press SELECT to switch between QNH, OAT, and ELEV. Use UP and DOWN to change the active value. Long press UP to toggle between fine and coarse steps. Press BACK to exit. Touch controls Tap − or + to decrease or increase the active value. Tap and hold for larger steps. Tap the lower half of the screen to switch to the next input field. Step sizes (fine / coarse) QNH: 1 hPa or 0.01 inHg / 5 hPa or 0.05 inHg OAT: 1° / 5° ELEV: 10 ft / 100 ft