*******************************************************************************/ECEFT satpos_ephemeris(double t, char n){  double ei,ea,diff,ta,aol,delr,delal,delinc,r,inc;  double la,xp,yp,bclk,tc,d_toc,d_toe;  double xn,yn,zn,xe,ye,xls,yls,zls,range1,ralt,tdot,satang,xaz,yaz;  double b,az;  ECEFT result;////     MA IS THE ANGLE FROM PERIGEE AT TOA//  d_toc = t-gps_eph[n].toc;  if ( d_toc>302400.0)     d_toc = d_toc-604800.0;  else if (d_toc<-302400.0)    d_toc=d_toc+604800.0;  bclk = gps_eph[n].af0 + gps_eph[n].af1*d_toc +          gps_eph[n].af2*d_toc*d_toc - gps_eph[n].tgd;  tc    = t - bclk;  d_toe = tc - gps_eph[n].toe;  if ( d_toe > 302400.0)     d_toe = d_toe-604800.0;  else if (d_toe < -302400.0)    d_toe = d_toe + 604800.0;  ei = gps_eph[n].ma + d_toe*gps_eph[n].wm + gps_eph[n].dn;  ea = ei;  do  {    diff = (ei-(ea-gps_eph[n].ety*sin(ea)))/(1.0E0-gps_eph[n].ety*cos(ea));    ea   = ea+diff;  } while ( fabs(diff) > 1.0e-9 );  bclk      = bclk-4.442807633E-10*gps_eph[n].ety*gps_eph[n].sqra*sin(ea);  result.tb = bclk;////     ea is the eccentric anomaly//  ta = atan2(sqrt(1.00-pow(gps_eph[n].ety,2))*sin(ea),cos(ea)-gps_eph[n].ety);////     TA IS THE TRUE ANOMALY (ANGLE FROM PERIGEE)//  aol = ta + gps_eph[n].w;////     AOL IS THE ARGUMENT OF LATITUDE OF THE SATELLITE////     calculate the second harmonic perturbations of the orbit//  delr   = gps_eph[n].crc*cos( 2.0*aol) + gps_eph[n].crs*sin( 2.0*aol);  delal  = gps_eph[n].cuc*cos( 2.0*aol) + gps_eph[n].cus*sin( 2.0*aol);  delinc = gps_eph[n].cic*cos( 2.0*aol) + gps_eph[n].cis*sin( 2.0*aol);////     R IS THE RADIUS OF SATELLITE ORBIT AT TIME T//  r   = pow(gps_eph[n].sqra,2)*(1.00-gps_eph[n].ety*cos(ea))+delr;  aol = aol+delal;  inc = gps_eph[n].inc0+delinc+gps_eph[n].idot*d_toe;//      WRITE(6,*)T-TOE(N)////     LA IS THE CORRECTED LONGITUDE OF THE ASCENDING NODE//  la = gps_eph[n].omega0 + (gps_eph[n].omegadot-omegae)*d_toe -       omegae*gps_eph[n].toe;  xp = r*cos(aol);  yp = r*sin(aol);  result.x  = xp*cos(la)-yp*cos(inc)*sin(la);  result.y  = xp*sin(la)+yp*cos(inc)*cos(la);  result.z  = yp*sin(inc);  result.az = 0.0;  result.el = 0.0;  if ( rec_pos_xyz.x != 0.0 || rec_pos_xyz.y != 0.0 || rec_pos_xyz.z != 0.0)  {//               fprintf(stream,"x=%20.10lf,y=%20.10lf,z=%20.10lf\n",rec_pos_xyz.x,//               rec_pos_xyz.y,rec_pos_xyz.z);/*      CALCULATE THE POSITION OF THE RECEIVER*/    xn  = -cos(rec_pos_llh.lon)*sin(rec_pos_llh.lat);    yn  = -sin(rec_pos_llh.lon)*sin(rec_pos_llh.lat);    zn  =  cos(rec_pos_llh.lat);    xe  = -sin(rec_pos_llh.lon);    ye  =  cos(rec_pos_llh.lon);/*     DETERMINE IF A CLEAR LINE OF SIGHT EXISTS*/    xls = result.x-rec_pos_xyz.x;    yls = result.y-rec_pos_xyz.y;    zls = result.z-rec_pos_xyz.z;    range1 = sqrt(xls*xls+yls*yls+zls*zls);    ralt = sqrt(rec_pos_xyz.x*rec_pos_xyz.x+rec_pos_xyz.y*rec_pos_xyz.y+rec_pos_xyz.z*rec_pos_xyz.z);    tdot = (rec_pos_xyz.x*xls+rec_pos_xyz.y*yls+rec_pos_xyz.z*zls)/range1/ralt;    xls = xls/range1;    yls = yls/range1;    zls = zls/range1;    if ( tdot >= 1.00 )       b=0.0;    else if ( tdot <= -1.00 )       b=pi;    else    {       b=acos(tdot);    }    satang=pi/2.0-b;    xaz=xe*xls+ye*yls;    yaz=xn*xls+yn*yls+zn*zls;    if (xaz !=0.0 || yaz !=0.0)       az = atan2(xaz,yaz);    else       az = 0.0;    result.el = satang;    result.az = az;  }  return result;}/*******************************************************************************FUNCTION read_initial_data()RETURNS  None.PARAMETERS None.PURPOSEWRITTEN BY  Clifford Kelley*******************************************************************************/void read_initial_data(void){  int   id;  SATVIS dummy;    for (id=1; id<=32; id++)     gps_alm[id].inc = 0.0;////  READ THE INPUT DATA FILE(s)//// for initialization, if we have data we will switch to warm or hot start  status = cold_start;         read_ion_utc();  read_almanac();  dummy = satfind( 0);  read_ephemeris();  thetime = time( NULL);//  printf( "thetime = %d\n", thetime);//  getchar();  return;}/*******************************************************************************FUNCTION receiver_loc()RETURNS  None.PARAMETERS None.PURPOSEWRITTEN BY  Clifford Kelley*******************************************************************************/LLH receiver_loc( void){  float latitude, longitude, height;  char  text[10];  LLH   result;  FILE  *in;  result.lat = 0.0;  result.lon = 0.0;  result.hae = 0.0;/* *    READ THE CURRENT LOCATION DATA FILE */  char infile[] = "curloc.dat";  char *tmpstr;  tmpstr = conmalloc( strlen( OGSDataDir) + strlen( infile) + 1);  strcpy( tmpstr, OGSDataDir);  strcat( tmpstr, infile);  if ((in = fopen( tmpstr, "rt")) == NULL)  {    printf( "error opening %s.\n", tmpstr);    status = cold_start;  }  else  {    fscanf( in, "%10s", text);    fscanf( in, "%f", &latitude);    fscanf( in, "%10s", text);    fscanf( in, "%f", &longitude);    fscanf( in, "%10s", text);    fscanf( in, "%f", &height);    result.lat = latitude / 57.296;    result.lon = longitude / 57.296;    result.hae = height;  }  fclose( in);  if ( tmpstr)    free( tmpstr);  return (result);}/*******************************************************************************FUNCTION navmess()RETURNS  None.PARAMETERS None.PURPOSE  This function assembles and decodes the 1500 bit nav message  into almanac and ephmeris messagesWRITTEN BY  Clifford Kelley*******************************************************************************/void decode_navmess( char prn, char ch){  int i,j,k;  unsigned long isqra, ie, iomega0;  long iaf0, iomegadot;  char itgd, iaf2;  int iweek, icapl2, iura, ihealth, iodc, iodct, iaf1;  unsigned int itoe, itoc;  int iode, icrs, idn, icuc, icus, fif, icic, iomegad;  int icis, icrc, idoe, idot;  unsigned int iae, iatoa;//  static i4page, i5page;  static int i4page, i5page;   // GB: int inserted  int   i4data, i5data, isv, iaomegad;  long  iaaf0, iaaf1, iadeli, iaomega0, im0, inc0, iw;  unsigned long iasqr;  long  iaw, iam0, scale, ia0, ia1;  char  ial0, ial1, ial2, ial3, ibt0, ibt1, ibt2, ibt3;  int   itot, iWNt, idtls, iWNlsf, iDN, idtlsf, WNa;  int   sfr, word, i4p, i5p;  float d_toe;////    assemble the bits into subframes and words//  d_toe = clock_tow - gps_eph[prn].toe;  if (d_toe > 302400.0)     d_toe = d_toe - 604800.0;  else if ( d_toe < -302400.0)    d_toe = d_toe + 604800.0;  if ( gps_eph[prn].valid==0 ||        (almanac_valid==0 && almanac_flag==0) ||        fabs( d_toe) > 7200.0)  {    j=0;    for ( sfr=1; sfr<=5; sfr++)    {      for ( word=1;word<=10;word++)      {        scale         = 536870912L;  // 2^29        sf[sfr][word] = 0;        for ( i=0;i<=29;i++)        {          if ( chan[ch].message[(j+chan[ch].offset)%1500] == 1)            sf[sfr][word] += scale;          scale = scale>>1;          j++;        }      }    }    parity_check(); // check the parity of the 1500 bit message////   EPHEMERIS DECODE subframes 1, 2, 3////  subframe 1//    if ((p_error[1]==0 || p_error[1]==0x200) && p_error[2]==0 && p_error[3]==0)    {      gps_eph[prn].valid=0;      iodc = (int)(((sf[1][3] & 0x3) <<8 ) | ((sf[1][8] & 0xFF0000L) >> 16));//    iodct=iodc & 0xff;//    iode=sf[2][3]  >> 16;//    idoe=sf[3][10] >> 16;//    if ( iodct != iode || iodct!= idoe || iode != idoe || gps_eph[prn].sqra==0.0)//          iweek               = (int)(sf[1][3] >> 14);      gps_eph[prn].week   = iweek;//      icapl2              = ( sf[1][3] & 0x3000 ) >> 12;      iura                = (int)(( sf[1][3] & 0xF00 ) >> 8);      gps_eph[prn].ura    = iura;      ihealth             = (int)(( sf[1][3] & 0xFC ) >> 2);      gps_eph[prn].health = ihealth;      gps_eph[prn].iodc   = iodc;      itgd                = (int)( sf[1][7] & 0xFF);      gps_eph[prn].tgd    = itgd*4.656612873e-10;      itoc                = (int)( sf[1][8] & 0xFFFF);      gps_eph[prn].toc    = itoc*16.0;      iaf2                = (int)( sf[1][9] >> 16);      gps_eph[prn].af2    = iaf2*2.775557562e-17;      iaf1                = (int)( sf[1][9] & 0xFFFF);      gps_eph[prn].af1    = iaf1*1.136868377e-13;      iaf0                = sf[1][10] >> 2;      if ( bit_test_l( iaf0, 22))         iaf0 = iaf0 | 0xFFC00000L;      gps_eph[prn].af0    = iaf0*4.656612873e-10;////   subframe 2//      icrs = (int)(sf[2][3] & 0xFFFF);      gps_eph[prn].crs      = icrs*.03125;      idn                   = (int)(sf[2][4] >> 8);      gps_eph[prn].dn       = idn*1.136868377e-13*pi;      im0                   = ((sf[2][4] & 0xFF) << 24) | sf[2][5];      gps_eph[prn].ma       = im0*4.656612873e-10*pi;      icuc                  = (int)(sf[2][6] >>8);      gps_eph[prn].cuc      = icuc*1.862645149e-9;      ie                    = ((sf[2][6] & 0xFF) << 24) | sf[2][7];      gps_eph[prn].ety      = ie*1.164153218e-10;      icus                  = (int)(sf[2][8] >> 8);      gps_eph[prn].cus      = icus*1.862645149e-9;      isqra                 = (((sf[2][8] & 0xFF) << 24) | sf[2][9]);      gps_eph[prn].sqra     = isqra*1.907348633e-6;      if (gps_eph[prn].sqra>0.0)         gps_eph[prn].wm     = 19964981.84/pow(gps_eph[prn].sqra,3);      itoe                  = (int)(sf[2][10] >> 8);      gps_eph[prn].toe      = itoe*16.;//      fif=(sf[2][10] & 0x80) >> 7;//// subframe 3//      icic                  = (int)(sf[3][3] >> 8);      gps_eph[prn].cic      = icic*1.862645149e-9;      icis                  = (int)(sf[3][5] >> 8);      gps_eph[prn].cis      = icis*1.862645149e-9;      inc0                  = ((sf[3][5] & 0xFF) << 24) | sf[3][6];      gps_eph[prn].inc0     = inc0*4.656612873e-10*pi;      iomega0               = ((sf[3][3] & 0xFF) << 24) | sf[3][4];      gps_eph[prn].omega0=iomega0*4.656612873e-10*pi;      icrc=(int)(sf[3][7] >> 8);      gps_eph[prn].crc=icrc*.03125;      iw=((sf[3][7] & 0xFF) << 24) | sf[3][8];      gps_eph[prn].w=iw*4.656612873e-10*pi;      iomegadot=sf[3][9];      if (bit_test_l(iomegadot,24))         iomegadot=iomegadot | 0xFF000000L;      gps_eph[prn].omegadot=iomegadot*1.136868377e-13*pi;      idot=(int)((sf[3][10] & 0xFFFC) >> 2);      if (bit_test_l(idot,14))         idot=idot | 0xC000;      gps_eph[prn].idot=idot*1.136868377e-13*pi;      if ( gps_eph[prn].inc0 != 0.0 &&            gps_eph[prn].sqra > 5000.0 &&           gps_eph[prn].ety < .05)         gps_eph[prn].valid = 1;    }////    ALMANAC DECODE  subframes 4 and 5////    SUBFRAME 4//    if (p_error[4]==0 && p_error[5]==0 && almanac_valid==0 && almanac_flag==0)    {      almanac_flag=1;//      i4data= sf[4][3] >> 22;      i4p = (int)((sf[4][3] & 0x3F0000L) >> 16);      if ( i4p != i4page)      {        i4page=i4p;        if (i4page > 24 && i4page < 33)        {          isv=i4page ;          gps_alm[isv].week=gps_week;          iae=(int)(sf[4][3] & 0x00FFFFL);          gps_alm[isv].ety=iae*4.768371582E-7;          iatoa=(int)(sf[4][4] >> 16);          gps_alm[isv].toa=iatoa*4096.0;          iadeli=sf[4][4] & 0x00FFFFL;          if (bit_test_l(iadeli,16))             iadeli=iadeli | 0xFFFF0000L;          gps_alm[isv].inc=(iadeli*1.907348633E-6+0.3)*pi;          iomegad=(int)(sf[4][5] >> 8);          gps_alm[isv].omegadot=iomegad*3.637978807E-12*pi;          gps_alm[isv].health=(int)(sf[4][5] & 0x0000FF);          iasqr=sf[4][6];          gps_alm[isv].sqra=iasqr*4.8828125E-4;          if (gps_alm[isv].sqra>0.0)             gps_alm[isv].w=19964981.84/pow(gps_alm[isv].sqra,3);          iaomega0=sf[4][7];          if (bit_test_l(iaomega0,24))             iaomega0=iaomega0 | 0xFF000000L;          gps_alm[isv].omega0=iaomega0*1.192092896E-7*pi;          iaw=sf[4][8];          if (bit_test_l(iaw,24))             iaw=iaw | 0xFF000000L;          gps_alm[isv].w=iaw*1.192092896E-7*pi;          iam0=sf[4][9];          if (bit_test_l(iam0,24))             iam0=iam0 | 0xFF000000L;            gps_alm[isv].ma=iam0*1.192092896E-7*pi;//          iaaf0=(sf[4][10] >> 13) | (sf[4][10] & 0x1C);            iaaf0=(sf[4][10] >> 13) | ((sf[4][10] & 0x1C) >> 2);  // fixed (GB-020217)            if (bit_test_l(iaaf0,11))             iaaf0=iaaf0 | 0xFFFFF800L;          gps_alm[isv].af0=iaaf0*9.536743164E-7;          iaaf1=(sf[4][10] | 0xFFE0) >> 5;          if (bit_test_l(iaaf1,11))             iaaf1=iaaf1 | 0xFFFFF800L;          gps_alm[isv].af1=iaaf1*3.637978807E-12;        }        else if ( i4page == 55 )        {