source: ntrip/trunk/BNC/src/RTCM3/ephEncoder.cpp@ 8812

#include "ephEncoder.h"

using namespace std;


// build up RTCM3 for GPS
////////////////////////////////////////////////////////////////////////////
int t_ephEncoder::RTCM3(const t_ephGPS& eph, unsigned char *buffer) {

  unsigned char *startbuffer = buffer;
  buffer= buffer+3;
  int size = 0;
  int numbits = 0;
  unsigned long long bitbuffer = 0;
  int ura = indexFromAccuracy(eph._ura, eph.type());
  int L5Flag, SFlag;

  if (eph.type() == t_eph::QZSS) {
    GPSADDBITS(12, 1044)
    GPSADDBITS(4, eph._prn.number())
    GPSADDBITS(16, static_cast<int>(eph._TOC.gpssec())>>4)
    GPSADDBITSFLOAT(8, eph._clock_driftrate, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<25))
    GPSADDBITSFLOAT(16, eph._clock_drift, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<13))
    GPSADDBITSFLOAT(22, eph._clock_bias, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<1))
    GPSADDBITS(8, eph._IODE)
    GPSADDBITSFLOAT(16, eph._Crs, 1.0/static_cast<double>(1<<5))
    GPSADDBITSFLOAT(16, eph._Delta_n, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<13))
    GPSADDBITSFLOAT(32, eph._M0, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
    GPSADDBITSFLOAT(16, eph._Cuc, 1.0/static_cast<double>(1<<29))
    GPSADDBITSFLOAT(32, eph._e, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<3))
    GPSADDBITSFLOAT(16, eph._Cus, 1.0/static_cast<double>(1<<29))
    GPSADDBITSFLOAT(32, eph._sqrt_A, 1.0/static_cast<double>(1<<19))
    GPSADDBITS(16, static_cast<int>(eph._TOEsec)>>4)
    GPSADDBITSFLOAT(16, eph._Cic, 1.0/static_cast<double>(1<<29))
    GPSADDBITSFLOAT(32, eph._OMEGA0, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
    GPSADDBITSFLOAT(16, eph._Cis, 1.0/static_cast<double>(1<<29))
    GPSADDBITSFLOAT(32, eph._i0, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
    GPSADDBITSFLOAT(16, eph._Crc, 1.0/static_cast<double>(1<<5))
    GPSADDBITSFLOAT(32, eph._omega, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
    GPSADDBITSFLOAT(24, eph._OMEGADOT, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<13))
    GPSADDBITSFLOAT(14, eph._IDOT, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<13))
    GPSADDBITS(2,eph._L2Codes)
    GPSADDBITS(10, eph._TOC.gpsw())
    GPSADDBITS(4, ura)
    GPSADDBITS(6, eph._health)
    GPSADDBITSFLOAT(8, eph._TGD, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<1))
    GPSADDBITS(10, eph._IODC)
    GPSADDBITS(1, eph._fitInterval)
    GPSADDBITS(3, 0) /* padding */
  } else if (eph.type() == t_eph::IRNSS) {
    GPSADDBITS(12, 29)
    GPSADDBITS(6, eph._prn.number())
    GPSADDBITS(10, eph._TOC.gpsw())
    GPSADDBITSFLOAT(22, eph._clock_bias, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<1))
    GPSADDBITSFLOAT(16, eph._clock_drift, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<13))
    GPSADDBITSFLOAT(8, eph._clock_driftrate, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<25))
    GPSADDBITS(4, ura)
    GPSADDBITS(16, static_cast<int>(eph._TOC.gpssec())>>4)
    GPSADDBITSFLOAT(8, eph._TGD, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<1))
    GPSADDBITSFLOAT(22, eph._Delta_n, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<11))
    GPSADDBITS(8, eph._IODE) // Issue Of Data Ephemeris and Clock
    GPSADDBITS(10, 0) /* padding */
    if        (eph._health == 0.0) {
      L5Flag = 0;
      SFlag  = 0;
    } else if (eph._health == 1.0) {
      L5Flag = 0;
      SFlag  = 1;
    } else if (eph._health == 2.0) {
      L5Flag = 1;
      SFlag  = 0;
    } else if (eph._health == 3.0) {
      L5Flag = 1;
      SFlag  = 1;
    }
    GPSADDBITS(1, L5Flag)
    GPSADDBITS(1, SFlag)
    GPSADDBITSFLOAT(15, eph._Cuc, 1.0/static_cast<double>(1<<28))
    GPSADDBITSFLOAT(15, eph._Cus, 1.0/static_cast<double>(1<<28))
    GPSADDBITSFLOAT(15, eph._Cic, 1.0/static_cast<double>(1<<28))
    GPSADDBITSFLOAT(15, eph._Cis, 1.0/static_cast<double>(1<<28))
    GPSADDBITSFLOAT(15, eph._Crc, 1.0/static_cast<double>(1<< 4))
    GPSADDBITSFLOAT(15, eph._Crs, 1.0/static_cast<double>(1<< 4))
    GPSADDBITSFLOAT(14, eph._IDOT, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<13))
    GPSADDBITSFLOAT(32, eph._M0, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
    GPSADDBITS(16, static_cast<int>(eph._TOEsec)>>4)
    GPSADDBITSFLOAT(32, eph._e, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<3))
    GPSADDBITSFLOAT(32, eph._sqrt_A, 1.0/static_cast<double>(1<<19))
    GPSADDBITSFLOAT(32, eph._OMEGA0, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
    GPSADDBITSFLOAT(32, eph._omega, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
    GPSADDBITSFLOAT(22, eph._OMEGADOT, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<11))
    GPSADDBITSFLOAT(32, eph._i0, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
    GPSADDBITS(2, 0) /* padding */
    GPSADDBITS(2, 0) /* padding */
  } else {
    GPSADDBITS(12, 1019)
    GPSADDBITS(6,eph._prn.number())
    GPSADDBITS(10, eph._TOC.gpsw())
    GPSADDBITS(4, ura)
    GPSADDBITS(2,eph._L2Codes)
    GPSADDBITSFLOAT(14, eph._IDOT, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<13))
    GPSADDBITS(8, eph._IODE)
    GPSADDBITS(16, static_cast<int>(eph._TOC.gpssec())>>4)
    GPSADDBITSFLOAT(8, eph._clock_driftrate, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<25))
    GPSADDBITSFLOAT(16, eph._clock_drift, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<13))
    GPSADDBITSFLOAT(22, eph._clock_bias, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<1))
    GPSADDBITS(10, eph._IODC)
    GPSADDBITSFLOAT(16, eph._Crs, 1.0/static_cast<double>(1<<5))
    GPSADDBITSFLOAT(16, eph._Delta_n, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<13))
    GPSADDBITSFLOAT(32, eph._M0, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
    GPSADDBITSFLOAT(16, eph._Cuc, 1.0/static_cast<double>(1<<29))
    GPSADDBITSFLOAT(32, eph._e, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<3))
    GPSADDBITSFLOAT(16, eph._Cus, 1.0/static_cast<double>(1<<29))
    GPSADDBITSFLOAT(32, eph._sqrt_A, 1.0/static_cast<double>(1<<19))
    GPSADDBITS(16, static_cast<int>(eph._TOEsec)>>4)
    GPSADDBITSFLOAT(16, eph._Cic, 1.0/static_cast<double>(1<<29))
    GPSADDBITSFLOAT(32, eph._OMEGA0, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
    GPSADDBITSFLOAT(16, eph._Cis, 1.0/static_cast<double>(1<<29))
    GPSADDBITSFLOAT(32, eph._i0, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
    GPSADDBITSFLOAT(16, eph._Crc, 1.0/static_cast<double>(1<<5))
    GPSADDBITSFLOAT(32, eph._omega, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
    GPSADDBITSFLOAT(24, eph._OMEGADOT, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<13))
    GPSADDBITSFLOAT(8, eph._TGD, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<1))
    GPSADDBITS(6, eph._health)
    GPSADDBITS(1, eph._L2PFlag)
    GPSADDBITS(1, eph._fitInterval)
  }

  startbuffer[0]=0xD3;
  startbuffer[1]=(size >> 8);
  startbuffer[2]=size;
  unsigned long  i = CRC24(size+3, startbuffer);
  buffer[size++] = i >> 16;
  buffer[size++] = i >> 8;
  buffer[size++] = i;
  size += 3;
  return size;
}

// build up RTCM3 for GLONASS
////////////////////////////////////////////////////////////////////////////
int t_ephEncoder::RTCM3(const t_ephGlo& eph, unsigned char *buffer)
{

  int size = 0;
  int numbits = 0;
  long long bitbuffer = 0;
  unsigned char *startbuffer = buffer;
  buffer= buffer+3;

  GLONASSADDBITS(12, 1020)
  GLONASSADDBITS(6, eph._prn.number())
  GLONASSADDBITS(5, 7+eph._frequency_number)
  GLONASSADDBITS(1, eph._almanac_health)
  GLONASSADDBITS(1, eph._almanac_health_availablility_indicator)
  GLONASSADDBITS(2, eph._P1)
  int tki = static_cast<int>(eph._tki)+3*60*60;
  if (tki > 86400) {tki -= 86400;}
  GLONASSADDBITS(5, static_cast<int>(tki)/(60*60))
  GLONASSADDBITS(6, (static_cast<int>(tki)/60)%60)
  GLONASSADDBITS(1, (static_cast<int>(tki)/30)%30)
  GLONASSADDBITS(1, eph._health)
  GLONASSADDBITS(1, eph._P2)
  unsigned long long timeofday = (static_cast<int>(eph._tt.gpssec()+3*60*60-eph._gps_utc)%86400);
  GLONASSADDBITS(7, timeofday/60/15)
  GLONASSADDBITSFLOATM(24, eph._x_velocity*1000, 1000.0/static_cast<double>(1<<20))
  GLONASSADDBITSFLOATM(27, eph._x_pos*1000, 1000.0/static_cast<double>(1<<11))
  GLONASSADDBITSFLOATM(5, eph._x_acceleration*1000, 1000.0/static_cast<double>(1<<30))
  GLONASSADDBITSFLOATM(24, eph._y_velocity*1000, 1000.0/static_cast<double>(1<<20))
  GLONASSADDBITSFLOATM(27, eph._y_pos*1000, 1000.0/static_cast<double>(1<<11))
  GLONASSADDBITSFLOATM(5, eph._y_acceleration*1000, 1000.0/static_cast<double>(1<<30))
  GLONASSADDBITSFLOATM(24, eph._z_velocity*1000, 1000.0/static_cast<double>(1<<20))
  GLONASSADDBITSFLOATM(27,eph._z_pos*1000, 1000.0/static_cast<double>(1<<11))
  GLONASSADDBITSFLOATM(5, eph._z_acceleration*1000, 1000.0/static_cast<double>(1<<30))
  GLONASSADDBITS(1, eph._P3)
  GLONASSADDBITSFLOATM(11, eph._gamma, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<10))
  GLONASSADDBITS(2, eph._M_P) /* GLONASS-M P */
  GLONASSADDBITS(1, eph._M_l3) /* GLONASS-M ln(3) */
  GLONASSADDBITSFLOATM(22, eph._tau, 1.0/static_cast<double>(1<<30))
  GLONASSADDBITSFLOATM(5, eph._M_delta_tau, 1.0/static_cast<double>(1<<30)) /* GLONASS-M delta tau */
  GLONASSADDBITS(5, eph._E)
  GLONASSADDBITS(1, eph._M_P4) /* GLONASS-M P4 */
  GLONASSADDBITS(4, eph._M_FT) /* GLONASS-M FT */
  GLONASSADDBITS(11, eph._M_NT) /* GLONASS-M NT */
  GLONASSADDBITS(2, eph._M_M) /* GLONASS-M active? */
  GLONASSADDBITS(1, eph._additional_data_availability) /* GLONASS additional data */
  GLONASSADDBITS(11, eph._NA) /* GLONASS NA */
  GLONASSADDBITSFLOATM(32, eph._tauC, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<1)) /* GLONASS tau C */
  GLONASSADDBITS(5, eph._M_N4) /* GLONASS-M N4 */
  GLONASSADDBITSFLOATM(22, eph._M_tau_GPS, 1.0/static_cast<double>(1<<30)) /* GLONASS-M tau GPS */
  GLONASSADDBITS(1, eph._M_l5) /* GLONASS-M ln(5) */
  GLONASSADDBITS(7, 0) /* Reserved */

  startbuffer[0]=0xD3;
  startbuffer[1]=(size >> 8);
  startbuffer[2]=size;
  unsigned long i = CRC24(size+3, startbuffer);
  buffer[size++] = i >> 16;
  buffer[size++] = i >> 8;
  buffer[size++] = i;
  size += 3;
  return size;
}

// build up RTCM3 for Galileo
////////////////////////////////////////////////////////////////////////////
int t_ephEncoder::RTCM3(const t_ephGal& eph, unsigned char *buffer) {
  int size = 0;
  int numbits = 0;
  long long bitbuffer = 0;
  unsigned char *startbuffer = buffer;
  buffer= buffer+3;

  int SISA = indexFromAccuracy(eph._SISA, eph.type());

  GALILEOADDBITS(12, eph._inav ? 1046 : 1045)
  GALILEOADDBITS(6, eph._prn.number())
  GALILEOADDBITS(12, eph._TOC.galw())
  GALILEOADDBITS(10, eph._IODnav)
  GALILEOADDBITS(8, SISA)
  GALILEOADDBITSFLOAT(14, eph._IDOT, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<13))
  GALILEOADDBITS(14, eph._TOC.gpssec()/60)
  GALILEOADDBITSFLOAT(6, eph._clock_driftrate, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<29))
  GALILEOADDBITSFLOAT(21, eph._clock_drift, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<16))
  GALILEOADDBITSFLOAT(31, eph._clock_bias, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<4))
  GALILEOADDBITSFLOAT(16, eph._Crs, 1.0/static_cast<double>(1<<5))
  GALILEOADDBITSFLOAT(16, eph._Delta_n, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<13))
  GALILEOADDBITSFLOAT(32, eph._M0, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
  GALILEOADDBITSFLOAT(16, eph._Cuc, 1.0/static_cast<double>(1<<29))
  GALILEOADDBITSFLOAT(32, eph._e, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<3))
  GALILEOADDBITSFLOAT(16, eph._Cus, 1.0/static_cast<double>(1<<29))
  GALILEOADDBITSFLOAT(32, eph._sqrt_A, 1.0/static_cast<double>(1<<19))
  GALILEOADDBITS(14, eph._TOEsec/60)
  GALILEOADDBITSFLOAT(16, eph._Cic, 1.0/static_cast<double>(1<<29))
  GALILEOADDBITSFLOAT(32, eph._OMEGA0, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
  GALILEOADDBITSFLOAT(16, eph._Cis, 1.0/static_cast<double>(1<<29))
  GALILEOADDBITSFLOAT(32, eph._i0, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
  GALILEOADDBITSFLOAT(16, eph._Crc, 1.0/static_cast<double>(1<<5))
  GALILEOADDBITSFLOAT(32, eph._omega, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
  GALILEOADDBITSFLOAT(24, eph._OMEGADOT, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<13))
  GALILEOADDBITSFLOAT(10, eph._BGD_1_5A, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<2))
  if(eph._inav)
  {
    GALILEOADDBITSFLOAT(10, eph._BGD_1_5B, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<2))
    GALILEOADDBITS(2, static_cast<int>(eph._E5bHS))
    GALILEOADDBITS(1, eph._e5bDataInValid ? 1 : 0)
    GALILEOADDBITS(2, static_cast<int>(eph._E1_bHS))
    GALILEOADDBITS(1, eph._e1DataInValid ? 1 : 0)
  } else {
    GALILEOADDBITS(2, static_cast<int>(eph._E5aHS))
    GALILEOADDBITS(1,  eph._e5aDataInValid ? 1 : 0)
  }

  GALILEOADDBITS((eph._inav ? 2 : 7), 0)

  startbuffer[0]=0xD3;
  startbuffer[1]=(size >> 8);
  startbuffer[2]=size;
  unsigned long i = CRC24(size+3, startbuffer);
  buffer[size++] = i >> 16;
  buffer[size++] = i >> 8;
  buffer[size++] = i;
  size += 3;
  return size;
}

// build up RTCM3 for SBAS
////////////////////////////////////////////////////////////////////////////
int t_ephEncoder::RTCM3(const t_ephSBAS& eph, unsigned char* buffer) {
  int size = 0;
  int numbits = 0;
  long long bitbuffer = 0;
  unsigned char *startbuffer = buffer;
  buffer= buffer+3;

  int ura = indexFromAccuracy(eph._ura, eph.type());
  SBASADDBITS(12, 1043)
  SBASADDBITS(6, eph._prn.number()-20)
  SBASADDBITS(8, eph._IODN)
  SBASADDBITS(13, static_cast<int>(eph._TOC.daysec())>>4)
  SBASADDBITS(4, ura)
  SBASADDBITSFLOAT(30, eph._x_pos, 0.08)
  SBASADDBITSFLOAT(30, eph._y_pos, 0.08)
  SBASADDBITSFLOAT(25, eph._z_pos, 0.4)
  SBASADDBITSFLOAT(17, eph._x_velocity, 0.000625)
  SBASADDBITSFLOAT(17, eph._y_velocity, 0.000625)
  SBASADDBITSFLOAT(18, eph._z_velocity, 0.004)
  SBASADDBITSFLOAT(10, eph._x_acceleration, 0.0000125)
  SBASADDBITSFLOAT(10, eph._y_acceleration, 0.0000125)
  SBASADDBITSFLOAT(10, eph._z_acceleration, 0.0000625)
  SBASADDBITSFLOAT(12, eph._agf0, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<1))
  SBASADDBITSFLOAT(8, eph._agf1, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<10))
  SBASADDBITS(2,0);

  startbuffer[0]=0xD3;
  startbuffer[1]=(size >> 8);
  startbuffer[2]=size;
  unsigned long i = CRC24(size+3, startbuffer);
  buffer[size++] = i >> 16;
  buffer[size++] = i >> 8;
  buffer[size++] = i;
  size += 3;
  return size;
}

// build up RTCM3 for BDS
////////////////////////////////////////////////////////////////////////////
int t_ephEncoder::RTCM3(const t_ephBDS& eph, unsigned char* buffer) {
  int size = 0;
  int numbits = 0;
  long long bitbuffer = 0;
  unsigned char *startbuffer = buffer;
  buffer= buffer+3;

  int URA = indexFromAccuracy(eph._URA, eph.type());
  BDSADDBITS(12, RTCM3ID_BDS)
  BDSADDBITS(6, eph._prn.number())
  BDSADDBITS(13, eph._TOC.bdsw())
  BDSADDBITS(4, URA);
  BDSADDBITSFLOAT(14, eph._IDOT, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<13))
  BDSADDBITS(5, eph._AODE)
  BDSADDBITS(17, static_cast<int>(eph._TOC.bdssec())>>3)
  BDSADDBITSFLOAT(11, eph._clock_driftrate, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<30)/static_cast<double>(1<<6))
  BDSADDBITSFLOAT(22, eph._clock_drift, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<20))
  BDSADDBITSFLOAT(24, eph._clock_bias, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<3))
  BDSADDBITS(5, eph._AODC)
  BDSADDBITSFLOAT(18, eph._Crs, 1.0/static_cast<double>(1<<6))
  BDSADDBITSFLOAT(16, eph._Delta_n, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<13))
  BDSADDBITSFLOAT(32, eph._M0, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
  BDSADDBITSFLOAT(18, eph._Cuc, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<1))
  BDSADDBITSFLOAT(32, eph._e, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<3))
  BDSADDBITSFLOAT(18, eph._Cus, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<1))
  BDSADDBITSFLOAT(32, eph._sqrt_A, 1.0/static_cast<double>(1<<19))
  BDSADDBITS(17, static_cast<int>(eph._TOE.bdssec())>>3)
  BDSADDBITSFLOAT(18, eph._Cic, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<1))
  BDSADDBITSFLOAT(32, eph._OMEGA0, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
  BDSADDBITSFLOAT(18, eph._Cis, 1.0/static_cast<double>(1<<30)/static_cast<double>(1<<1))
  BDSADDBITSFLOAT(32, eph._i0, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
  BDSADDBITSFLOAT(18, eph._Crc, 1.0/static_cast<double>(1<<6))
  BDSADDBITSFLOAT(32, eph._omega, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<1))
  BDSADDBITSFLOAT(24, eph._OMEGADOT, M_PI/static_cast<double>(1<<30)/static_cast<double>(1<<13))
  BDSADDBITSFLOAT(10, eph._TGD1, 0.0000000001)
  BDSADDBITSFLOAT(10, eph._TGD2, 0.0000000001)
  BDSADDBITS(1, eph._SatH1)
  BDSADDBITS(1, 0) /* reserved bit, fill up 8 bits */

  startbuffer[0]=0xD3;
  startbuffer[1]=(size >> 8);
  startbuffer[2]=size;
  unsigned long i = CRC24(size+3, startbuffer);
  buffer[size++] = i >> 16;
  buffer[size++] = i >> 8;
  buffer[size++] = i;
  size += 3;
  return size;
}