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# atmosisa

Use International Standard Atmosphere model

## Syntax

```[T, a, P, rho] = atmosisa(height) ```

## Description

```[T, a, P, rho] = atmosisa(height)``` implements the mathematical representation of the International Standard Atmosphere values for ambient temperature, pressure, density, and speed of sound for the input geopotential altitude.

This function assumes that below the geopotential altitude of 0 km and above the geopotential altitude of the tropopause (at 20 km), temperature and pressure values are held constant.

## Input Arguments

 `height` Array of `m`-by-1 geopotential heights, in meters.

## Output Arguments

 `T` Array of `m` temperatures, in kelvin. `a` Array of `m` speeds of sound, in meters per second. The function calculates speed of sound using a perfect gas relationship. `rho` Array of `m` densities, in kilograms per meter cubed. The function calculates density using a perfect gas relationship. `P` Array of `m` pressures, in pascal.

## Examples

Calculate the International Standard Atmosphere at 1000 m:

```[T, a, P, rho] = atmosisa(1000) T = 281.6500 a = 336.4341 P = 8.9875e+004 rho = 1.1116```

Calculate the International Standard Atmosphere at 1000, 11,000, and 20,000 m:

```[T, a, P, rho] = atmosisa([1000 11000 20000]) T = 281.6500 216.6500 216.6500 a = 336.4341 295.0696 295.0696 P = 1.0e+004 * 8.9875 2.2632 0.5475 rho = 1.1116 0.3639 0.0880```

## References

U.S. Standard Atmosphere, 1976, U.S. Government Printing Office, Washington, D.C. 