#density-altitude

Aviation atmosphere maths as an API, computed locally and deterministically using the exact International Standard Atmosphere relations — the numbers a pilot, dispatcher or flight-planning tool needs before take-off, not a rough rule of thumb. The density-altitude endpoint turns the field elevation, altimeter setting and outside air temperature into the pressure altitude (elevation + (29.92 − setting) × 1000) and then the density altitude — the altitude the air actually feels like to the wings and engine — computed from the true ISA density ratio rather than the approximate 120-foot-per-degree rule, with the ISA temperature deviation: on a hot, high day the density altitude soars, robbing lift and thrust and lengthening the take-off roll, the classic mountain-airport hazard. The true-airspeed endpoint gives TAS from calibrated airspeed as CAS ÷ √(density ratio), so the navigator gets the real speed through the air that climbs above the indicated reading with altitude and temperature. The isa endpoint returns the standard-atmosphere temperature, pressure, pressure and density ratios and the speed of sound at any altitude in the troposphere — the reference every altimeter, performance chart and engine rating is built on. Everything is computed locally and deterministically, so it is instant and private. Ideal for flight-planning and EFB apps, drone and UAV tools, aviation weather dashboards, and aerospace-engineering utilities. Pure local computation — no key, no third-party service, instant. Troposphere (≤ 36,089 ft); incompressible TAS. 3 compute endpoints. For the speed of sound and Mach use a Mach-number API; for runway wind components a crosswind API.

api.oanor.com/densityaltitude-api

International Standard Atmosphere (ISA) maths as an API, computed locally and deterministically. The properties endpoint gives the air temperature, pressure, density and speed of sound at any altitude from sea level to 20 km — using the standard troposphere lapse rate (T = T0 − 0.0065·h) and the isothermal lower stratosphere above 11 km — along with the density, pressure and temperature ratios relative to sea level. The density-altitude endpoint computes the density altitude — the ISA altitude with the same air density — from a pressure altitude and the actual outside-air temperature, the figure pilots use because heat and low pressure rob an aircraft of lift, engine power and propeller thrust; it also reports the ISA temperature deviation. The pressure-altitude endpoint turns a barometric reading (in hectopascals or pascals) into the pressure altitude, the ISA altitude at which the standard pressure equals your reading. Altitudes accept metres or feet, temperature °C or kelvin. Everything is computed locally and deterministically, so it is instant and private. Ideal for aviation, drone, ballooning, HVAC and meteorology app developers, flight-planning and performance tools, and physics education. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This is the ISA atmospheric model; for the acoustic and relativistic Doppler effect use a Doppler API.

api.oanor.com/atmosphere-api