# ISAtmosphere.jl

`ISAtmosphere.ISAtmosphere`

— ModuleInternational Standard Atmospheric (ISA) model

The International Standard Atmosphere (ISA) is a static atmospheric model of how the pressure, temperature, density, and viscosity of the Earth's atmosphere change over a wide range of altitudes or elevations. It has been established to provide a common reference for temperature and pressure and consists of tables of values at various altitudes, plus some formulas by which those values were derived.

It is also known as the ICAO Standard Atmosphere, ISA is a standard against which to compare the actual atmosphere at any point and time. The real atmosphere differs from ISA in many ways. Sea level pressure varies from day to day, and there are wide extremes of temperature at all levels.

*Only metric units are used.*

Source: EUROCONTROL BADA 4 User Manual Chapter 2.2 Atmosphere Model

Source: www.skybrary.aero/index.php/International*Standard*Atmosphere_(ISA)

Source: en.wikipedia.org/wiki/International*Standard*Atmosphere

## Constants

`ISAtmosphere.Hp_trop_m`

— ConstantGeopotential pressure altitude [m] of Tropopause

`ISAtmosphere.R_M²_Ks²`

— ConstantReal gas constant for air [M²/(Ks²)]

`ISAtmosphere.T₀_K`

— ConstantStandard atmospheric temperature [K] at Mean Sea Level (MSL)

`ISAtmosphere.a₀_m_s`

— ConstantSpeed of sound [m/s] at Mean Sea Level (MSL)

`ISAtmosphere.g₀_m_s²`

— ConstantGraviation acceleration [m/s²] at Mean Sea Level (MSL)

`ISAtmosphere.p₀_Pa`

— ConstantStandard atmospheric pressure [Pa] at Mean Sea Level (MSL)

`ISAtmosphere.βT∇_K_m`

— ConstantISA temperature gradient [K/m] with altitude below the tropopause

`ISAtmosphere.κ`

— ConstantAdiabatic index of air []

`ISAtmosphere.ρ₀_kg_m³`

— ConstantStandard atmospheric density [kg/m³] at Mean Sea Level (MSL)

## Types

`ISAtmosphere.AtmosConditions`

— Type`AtmosConditions(Hp_m, T_K, ΔT_K, p_Pa, ρ_kg_m³, a_m_s)`

Immutable STRUCT to keep a set of atmospheric conditions together. This struct can be used to also store an arbitrary set of atmospheric conditions. The function `conditions`

can be used to create the struct.

## Functions

`ISAtmosphere.Hp_trans_m`

— Method`Hp_trans_m(Vcas_m_s, M)`

Return the transition altitude `Hp_trans_m`

(also called crossover altitude) [m] between a given calibrated airspeed `Vcas_m_s`

[m/s] and a Mach number `M`

.

Source: EUROCONTROL BADA 4 User Manual eq. 2.2-27/28/29

`ISAtmosphere.M2Vcas`

— Method`M2Vcas(M, p_Pa, T_K)`

Return the calibrated airspeed `Vcas_m_s`

[m/s] as a function of the Mach number `M`

at pressure level `p_Pa`

[Pa] and with temperature `T_K`

[K].

Source: EUROCONTROL BADA 4 User Manual eq. 2.2-26

`ISAtmosphere.M2Vcas`

— Method`M2Vcas(M, AtmosConditions)`

`ISAtmosphere.M2Vtas`

— Method`M2Vtas(M, T_K)`

Return true airspeed `Vtas_m_s`

[m/s] as a function of the Mach number `M`

and temperature `T_K`

[K].

Source: EUROCONTROL BADA 4 User Manual eq. 2.2-26

`ISAtmosphere.M2Vtas`

— Method`M2Vtas(M, AtmosConditions)`

`ISAtmosphere.T_K`

— Function`T_K(Hp_m [, ΔT_K= 0.0])`

Returns the atmospheric temperature [K] at pressure altitude `Hp_m`

[m] and with temperature offset `ΔT_K`

[K].

Source: EUROCONTROL BADA 4 User Manual eq. 2.2-13/16

`ISAtmosphere.Vcas2M`

— Method`Vcas2M(Vcas_m_s, T_K)`

Return the Mach number `M`

as a function of the calibrated airspeed `Vcas_m_s`

[m/s] at pressure level `p_Pa`

[Pa] and with temperature `T_K`

[K].

Source: EUROCONTROL BADA 4 User Manual eq. 2.2-26 (reversed)

`ISAtmosphere.Vcas2M`

— Method`Vcas2M(Vcas_m_s, AtmosConditions)`

`ISAtmosphere.Vcas2Vtas`

— Method`Vcas2Vtas(Vcas_m_s, p_Pa, T_K)`

Return the true airspeed `Vtas_m_s`

[m/s] as a function of the calibrated airspeed `Vcas_m_s`

[m/s] at pressure level `p_Pa`

[Pa] and with temperature `T_K`

[K].

Source: EUROCONTROL BADA 4 User Manual eq. 2.2-23

`ISAtmosphere.Vcas2Vtas`

— Method`Vcas2Vtas(Vcas_m_s, AtmosConditions)`

`ISAtmosphere.Vtas2M`

— Method`Vtas2M(Vtas_m_s, T_K)`

Return the Mach number `M`

as a function of the true airspeed `Vtas_m_s`

[m/s] and temperature `T_K`

[K].

Source: EUROCONTROL BADA 4 User Manual eq. 2.2-26 (reversed)

`ISAtmosphere.Vtas2M`

— Method`Vtas2M(Vtas_m_s, AtmosConditions)`

`ISAtmosphere.Vtas2Vcas`

— Method`Vtas2Vcas(Vtas_m_s, p_Pa, T_K)`

Return calibrated airspeed `Vcas_m_s`

[m/s] as a function of the true airspeed `Vtas_m_s`

[m/s] at pressure level `p_Pa`

[Pa] and with temperature `T_K`

[K].

Source: EUROCONTROL BADA 4 User Manual eq. 2.2-24

`ISAtmosphere.Vtas2Vcas`

— Method`Vtas2Vcas(Vtas_m_s, AtmosConditions)`

`ISAtmosphere.a_m_s`

— Method`a_m_s(T_K)`

Return the speed of sound [m/s] at the temperature `T_K`

[K].

Source: EUROCONTROL BADA 4 User Manual eq. 2.2-22

`ISAtmosphere.conditions`

— Function`conditions(Hp_m[, ΔT_K = 0.0])`

Create `AtmosConditions`

struct with the atmospheric conditions `T_K`

[K], `p_Pa`

[Pa], and `ρ_kg_m³`

[kg/m³], and the speed of sound `a_m_s`

[m/s] at a given altitude `Hp_m`

[m] and `ΔT_K`

[K] temperature offset.

`ISAtmosphere.p_Pa`

— Function`p_Pa(Hp_m[, ΔT_K = 0.0])`

Return the air pressure [Pa] at pressure altitude `Hp_m`

[m] and with temperature offset `ΔT_K`

[K].

Source: EUROCONTROL BADA 4 User Manual eq. 2.2-18/20

`ISAtmosphere.ρ_kg_m³`

— Method`ρ_kg_m³(p_Pa, T_K)`

Return the air density [kg/m³] at pressure level `p_Pa`

[Pa] and temperature `T_K`

[K].

Source: EUROCONTROL BADA 4 User Manual eq. 2.2-21