pressure.h

// Copyright 2009-2018 Toby Schneider (http://gobysoft.org/index.wt/people/toby)
//                     GobySoft, LLC (2013-)
//                     Massachusetts Institute of Technology (2007-2014)
//                     Community contributors (see AUTHORS file)
//
//
// This file is part of the Goby Underwater Autonomy Project Libraries
// ("The Goby Libraries").
//
// The Goby Libraries are free software: you can redistribute them and/or modify
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// the Free Software Foundation, either version 2.1 of the License, or
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// GNU Lesser General Public License for more details.
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// modified for C++ by s. petillo spetillo@mit.edu
// ocean engineering graduate student - mit / whoi joint program
// massachusetts institute of technology (mit)
// laboratory for autonomous marine sensing systems (lamss)

#ifndef PRESSUREH
#define PRESSUREH

#include <cmath>

// Calculate water density anomaly at a given Salinity, Temperature, Pressure using the seawater Equation of State.
// Taken directly from MATLAB OceansToolbox pressure.m

inline double depth2pressure(double DPTH, double XLAT)
{
    // function P80=pressure(DPTH,XLAT);
    /*
      Computes pressure given the depth at some latitude
      P = depth2pressure(DPTH,XLAT) gives the pressure P (dbars) at a depth DPTH (m) at some latitude XLAT (degrees).

      This probably works best in mid-latitude oceans, if anywhere!

      Ref: Saunders, "Practical Conversion of Pressure to Depth",
            J. Phys. Oceanog., April 1981.

      I copied this from the Matlab OceansToolbox pressure.m, copied directly from the UNESCO algorithms.


      CHECK VALUE: P80=7500.004 DBARS;FOR LAT=30 DEG., DEPTH=7321.45 METERS
                              ^P80 test value should be 7500.006 (from spetillo@mit.edu)
    */

    using namespace std; // for math functions

    const double pi = 3.14159;

    double PLAT = abs(XLAT * pi / 180);
    double D = sin(PLAT);
    double C1 = (5.92E-3) + (D * D) * (5.25E-3);
    double P80 = ((1 - C1) - sqrt(((1 - C1) * (1 - C1)) - ((8.84E-6) * DPTH))) / 4.42E-6;

    return P80;
}

#endif