Xvt.cpp

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//==============================================================================
//
//  This file is part of GNSSTk, the ARL:UT GNSS Toolkit.
//
//  The GNSSTk is free software; you can redistribute it and/or modify
//  it under the terms of the GNU Lesser General Public License as published
//  by the Free Software Foundation; either version 3.0 of the License, or
//  any later version.
//
//  The GNSSTk is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU Lesser General Public License for more details.
//
//  You should have received a copy of the GNU Lesser General Public
//  License along with GNSSTk; if not, write to the Free Software Foundation,
//  Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110, USA
//
//  This software was developed by Applied Research Laboratories at the
//  University of Texas at Austin.
//  Copyright 2004-2022, The Board of Regents of The University of Texas System
//
//==============================================================================
 
//==============================================================================
//
//  This software was developed by Applied Research Laboratories at the
//  University of Texas at Austin, under contract to an agency or agencies
//  within the U.S. Department of Defense. The U.S. Government retains all
//  rights to use, duplicate, distribute, disclose, or release this software.
//
//  Pursuant to DoD Directive 523024
//
//  DISTRIBUTION STATEMENT A: This software has been approved for public
//                            release, distribution is unlimited.
//
//==============================================================================
 
#include <tuple>
#include <iostream>
#include "Xvt.hpp"
#include "RawRange.hpp"
 
namespace gnsstk
{
 
   std::ostream& operator<<(std::ostream& os, const gnsstk::Xvt& xvt) noexcept
   {
      os << "x:" << xvt.x
         << ", v:" << xvt.v
         << ", clk bias:" << xvt.clkbias
         << ", clk drift:" << xvt.clkdrift
         << ", relcorr:" << xvt.relcorr
         << ", health:" << xvt.health
         << ", frame:" << xvt.frame;
      return os;
   }
 
   std::ostream& operator<<(std::ostream& os, const Xvt::HealthStatus& health)
      noexcept
   {
      switch (health)
      {
         case Xvt::Uninitialized:
            os << "Uninitialized";
            break;
         case Xvt::Unavailable:
            os << "Unavailable";
            break;
         case Xvt::Unused:
            os << "Unused";
            break;
         case Xvt::Unknown:
            os << "Unknown";
            break;
         case Xvt::Unhealthy:
            os << "Unhealthy";
            break;
         case Xvt::Degraded:
            os << "Degraded";
            break;
         case Xvt::Healthy:
            os << "Healthy";
            break;
         default:
            os << "???";
            break;
      }
      return os;
   }
 
      // compute the relativity correction
   double Xvt::computeRelativityCorrection(void)
   {
      relcorr = -2.0*( (x[0]/C_MPS)*(v[0]/C_MPS)
                       +(x[1]/C_MPS)*(v[1]/C_MPS)
                       +(x[2]/C_MPS)*(v[2]/C_MPS) );
      return relcorr;
   }
 
      // Function to find the range and position from a ground
      // location, rxPos, to the spacecraft position (*this).x
      // Use the pseudorange corrected for SV clock effects to get a
      // rough time of flight (dt).  Account directly for Earth
      // rotation, then compute a rough receiver bias by differencing
      // the initial time of flight with the new estimate.  Then
      // correct the rotation by a small amount.
   double Xvt::preciseRho(const Triple& rxPos,
                          const EllipsoidModel& ellips,
                          double correction) const
      noexcept
   {
         // Compute initial time of flight estimate using the
         // geometric range at transmit time.  This fails to account
         // for the rotation of the earth, but should be good to
         // within about 40 m
      double tofEstimate = rxPos.slantRange(x) / ellips.c();
 
      double range;
      std::tie(std::ignore, range, std::ignore) =
         RawRange::fromSvPos(rxPos, *this, ellips, true, tofEstimate, 0, 2);
 
      return range - (clkbias + relcorr) * ellips.c() - correction;
   }
 
} // end of gnsstk namespace