AshtechMBEN.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 "AshtechMBEN.hpp"
#include "AshtechStream.hpp"
#include "GNSSconstants.hpp"
 
using namespace std;
 
namespace gnsstk
 {
   const char* AshtechMBEN::mpcId = "MPC";
   const char* AshtechMBEN::mcaId = "MCA";
 
 
   //---------------------------------------------------------------------------
   void AshtechMBEN::reallyGetRecord(FFStream& ffs)
   {
      AshtechStream& stream=dynamic_cast<AshtechStream&>(ffs);
 
      // make sure the object is reset before starting the search
      clear(fmtbit | lenbit | crcbit);
      string& rawData = stream.rawData;
 
      // If this object doesn't have an id set yet, assume that the streams
      // most recent read id is what we need to be
      if (id == "" && rawData.size()>=11 &&
          rawData.substr(0,7) == preamble &&
          rawData[10]==',')
         id = rawData.substr(7,3);
 
      // If that didn't work, or this is object is not of the right type,
      // then give up.
      if (id == "" || !checkId(id))
         return;
 
      readBody(stream);
   }
 
 
   //---------------------------------------------------------------------------
   void AshtechMBEN::decode(const std::string& data)
   {
      using gnsstk::BinUtils::decodeVar;
 
      string str(data);
 
      uint8_t csum=0;
      if (str.length() == 108 || str.length()==52)
      {
         ascii=false;
         header = str.substr(0,11); str.erase(0,11);
 
         seq    = decodeVar<uint16_t>(str);
         left   = decodeVar<uint8_t>(str);
         svprn  = decodeVar<uint8_t>(str);
         el     = decodeVar<uint8_t>(str);
         az     = decodeVar<uint8_t>(str);
         chid   = decodeVar<uint8_t>(str);
 
         ca.decodeBIN(str);
 
         if (id == mpcId)
         {
            p1.decodeBIN(str);
            p2.decodeBIN(str);
         }
 
         checksum = decodeVar<uint8_t>(str);
 
         clear();
 
         int end = data.size() - 3;
         for (int i=11; i<end; i++)
            csum ^= data[i];
      }
      else
      {
         ascii=true;
         header = str.substr(0,11); str.erase(0,11);
         stringstream iss(str);
         char c;
         iss >> seq >> c
             >> left >> c
             >> svprn >> c
             >> el >> c
             >> az >> c
             >> chid >> c;
 
         ca.decodeASCII(iss);
 
         if (id == mpcId)
         {
            p1.decodeASCII(iss);
            p2.decodeASCII(iss);
         }
 
         iss >> checksum;
 
         if (iss)
            clear();
 
         int end=data.rfind(',');
         for (int i=11; i<=end; i++)
            csum ^= data[i];
      }
 
 
      if (csum != checksum)
      {
         setstate(crcbit);
         if (debugLevel)
            cout << "checksum error, computed:" << hex << (uint16_t) csum
                 << " received:" << checksum << dec << endl;
      }
 
      if (seq>36000)
         setstate(fmtbit);
   }
 
 
   //---------------------------------------------------------------------------
   void AshtechMBEN::code_block::decodeASCII(stringstream& str)
   {
      char c;
      str >> warning >> c
          >> goodbad >> c
          >> polarity_known>> c
          >> ireg >> c
          >> qa_phase >> c
          >> full_phase >> c
          >> raw_range >> c
          >> doppler >> c
          >> smoothing >> c
          >> smooth_cnt >> c;
 
      // The ashtech docs say this field should be in 1e-4 Hz
      // The data sure doesn't look like it, however
      //doppler *= 1e-4;
      raw_range *= 1e-3; //convert ms to sec
   }
 
 
   //---------------------------------------------------------------------------
   void AshtechMBEN::code_block::decodeBIN(string& str)
   {
      using gnsstk::BinUtils::decodeVar;
      uint32_t smo;
      warning        = decodeVar<uint8_t>(str);
      goodbad        = decodeVar<uint8_t>(str);
      polarity_known = decodeVar<uint8_t>(str);
      ireg           = decodeVar<uint8_t>(str);
      qa_phase       = decodeVar<uint8_t>(str);
      full_phase     = decodeVar<double>(str);
      raw_range      = decodeVar<double>(str);
      doppler        = decodeVar<int32_t>(str);
      smo            = decodeVar<uint32_t>(str);
 
      doppler *= 1e-4;
      smoothing = (smo & 0x800000 ? -1e-3 : 1e-3) * (smo & 0x7fffff);
      smooth_cnt = (smo >> 24) & 0xff;
   }
 
 
   //---------------------------------------------------------------------------
   void AshtechMBEN::code_block::dump(ostream& out) const
   {
      using gnsstk::StringUtils::asString;
      out << hex
          << "warn:" << (int)warning
          << " gb:" << (int)goodbad
          << " pol:" << (int)polarity_known
          << dec
          << " ireg:" << (int)ireg
          << " qa:" << (int)qa_phase
          << " phase:" << asString(full_phase, 1)
          << " range:" << asString(raw_range*1e3, 3)
          << " doppler:" << doppler
          << " smo:" << smoothing
          << " smo_cnt:" << smooth_cnt;
   }
 
 
   //---------------------------------------------------------------------------
   float AshtechMBEN::code_block::snr(float chipRate, float m) const noexcept
   {
      const float n = 20000;     // number of samples in 1 ms
      const float bw = 0.9 * chipRate; // equivalent noise bandwidth (Hz)
 
      const float d = PI/(n*n*m*m*4.0);
      float snr=0;
      // Note that ireg is as output from the MBEN which is 0-255, not the 0-99
      // as displayed on the front panel.
      if (ireg)
      {
         snr = exp(((float)ireg)/25.0);
         snr = snr*snr*bw*d;
         snr = 10 * log10(snr);
      }
 
      return snr;
   }
 
   //---------------------------------------------------------------------------
   void AshtechMBEN::dump(ostream& out) const noexcept
   {
      ostringstream oss;
      using gnsstk::StringUtils::asString;
 
      AshtechData::dump(oss);
      oss << getName() << "1:"
          << " seq:" << 0.05 * seq
          << " left:" << (int)left
          << " prn:" << (int)svprn
          << " el:" << (int)el
          << " az:" << (int)az
          << " chid:" << (int)chid
          << " " << (ascii?"ascii":"bin")
          << endl;
 
      oss << getName() << "2: ca ";
      ca.dump(oss);
      oss << endl;
 
      if (id == mpcId)
      {
         oss << getName() << "3: p1 ";
         p1.dump(oss);
         oss << endl;
         oss << getName() << "4: p2 ";
         p2.dump(oss);
         oss << endl;
      }
      out << oss.str() << flush;
   }
} // namespace gnsstk