# pvl_alt2pres

Determine site pressure from altitude

## Contents

- Syntax
- Description
- Assumptions
- Inputs
- Outputs
- Example
- References
- See Also

## Syntax

`pressure = pvl_alt2pres(altitude)`

## Description

Determines the atmospheric pressure (in Pascals) of a site on Earth's surface given its altitude (in meters above sea level). Output `Press` is given in Pascals. `Press` is of the same size as `altitude`.

## Assumptions

- Pressure at mean sea level = 101325 Pa
- Temperature at zero altitude = 288.15 K
- Gravitational acceleration = 9.80665 m/s^2
- Lapse rate = -6.5E-3 K/m
- Gas constant for air = 287.053 J/(kg*K)
- Relative Humidity = 0%

## Inputs

- `altitude` - altitude (in meters above sea level)

## Outputs

- `pressure` - atmospheric pressure (in Pascals) at a the Earth's surface at `altitude` above sea level

## Example

    Press1 = pvl_alt2pres(0) %Pressure at mean sea level
    Press2 = pvl_alt2pres(1000) % Pressure at 1,000 meters obove mean sea level

    Press1 =

       1.0132e+05

    Press2 =

       8.9875e+04

## References

[1] Portland State Aerospace Society, A Quick Derivation relating altitude to air pressure, Version 1.03, 12/22/2004, http://psas.pdx.edu/RocketScience/PressureAltitude_Derived.pdf

## See Also

`pvl_pres2alt` , `pvl_makelocationstruct`

Copyright 2014 Sandia National Laboratories