/* satellite position/clock by precise ephemeris/clock -------------------------
* compute satellite position/clock with precise ephemeris/clock
* args : gtime_t time I time (gpst)
* int sat I satellite number
* nav_t *nav I navigation data
* int opt I sat postion option
* (0: center of mass, 1: antenna phase center)
* double *rs O sat position and velocity (ecef)
* {x,y,z,vx,vy,vz} (m|m/s)
* double *dts O sat clock {bias,drift} (s|s/s)
* double *var IO sat position and clock error variance (m)
* (NULL: no output)
* return : status (1:ok,0:error or data outage)
* notes : clock includes relativistic correction but does not contain code bias
* before calling the function, nav->peph, nav->ne, nav->pclk and
* nav->nc must be set by calling readsp3(), readrnx() or readrnxt()
* if precise clocks are not set, clocks in sp3 are used instead
*-----------------------------------------------------------------------------*/
extern int peph2pos(gtime_t time, int sat, const nav_t *nav, int opt,
double *rs, double *dts, double *var)
{
double rss[3],rst[3],dtss[1],dtst[1],dant[3]={0},vare=0.0,varc=0.0,tt=1E-3;
int i;
trace(4,"peph2pos: time=%s sat=%2d opt=%d\n",time_str(time,3),sat,opt);
if (sat<=0||MAXSAT<sat) return 0;
/* satellite position and clock bias */
if (!pephpos(time,sat,nav,rss,dtss,&vare,&varc)||
!pephclk(time,sat,nav,dtss,&varc)) return 0;
time=timeadd(time,tt);
if (!pephpos(time,sat,nav,rst,dtst,NULL,NULL)||
!pephclk(time,sat,nav,dtst,NULL)) return 0;
/* satellite antenna offset correction */
if (opt) {
satantoff(time,rss,nav->pcvs+sat-1,dant);
}
for (i=0;i<3;i++) {
rs[i ]=rss[i]+dant[i];
rs[i+3]=(rst[i]-rss[i])/tt;
}
/* relativistic effect correction */
if (dtss[0]!=0.0) {
dts[0]=dtss[0]-2.0*dot(rs,rs+3,3)/CLIGHT/CLIGHT;
dts[1]=(dtst[0]-dtss[0])/tt;
}
else { /* no precise clock */
dts[0]=dts[1]=0.0;
}
if (var) *var=vare+varc;
return 1;
}
/* satellite position and clock with ssr correction --------------------------*/
static int satpos_ssr(gtime_t time, gtime_t teph, int sat, const nav_t *nav,
int opt, double *rs, double *dts, double *var, int *svh)
{
const ssr_t *ssr;
eph_t *eph;
double t1,t2,t3,er[3],ea[3],ec[3],rc[3],deph[3],dclk,dant[3]={0},tk;
int i,sys;
trace(4,"satpos_ssr: time=%s sat=%2d\n",time_str(time,3),sat);
ssr=nav->ssr+sat-1;
if (!ssr->t0[0].time) {
trace(2,"no ssr orbit correction: %s sat=%2d\n",time_str(time,0),sat);
return 0;
}
if (!ssr->t0[1].time) {
trace(2,"no ssr clock correction: %s sat=%2d\n",time_str(time,0),sat);
return 0;
}
/* inconsistency between orbit and clock correction */
if (ssr->iod[0]!=ssr->iod[1]) {
trace(2,"inconsist ssr correction: %s sat=%2d iod=%d %d\n",
time_str(time,0),sat,ssr->iod[0],ssr->iod[1]);
*svh=-1;
return 0;
}
t1=timediff(time,ssr->t0[0]);
t2=timediff(time,ssr->t0[1]);
t3=timediff(time,ssr->t0[2]);
/* ssr orbit and clock correction (ref [4]) */
if (fabs(t1)>MAXAGESSR||fabs(t2)>MAXAGESSR) {
trace(2,"age of ssr error: %s sat=%2d t=%.0f %.0f\n",time_str(time,0),
sat,t1,t2);
*svh=-1;
return 0;
}
if (ssr->udi[0]>=1.0) t1-=ssr->udi[0]/2.0;
if (ssr->udi[1]>=1.0) t2-=ssr->udi[0]/2.0;
for (i=0;i<3;i++) deph[i]=ssr->deph[i]+ssr->ddeph[i]*t1;
dclk=ssr->dclk[0]+ssr->dclk[1]*t2+ssr->dclk[2]*t2*t2;
/* ssr highrate clock correction (ref [4]) */
if (ssr->iod[0]==ssr->iod[2]&&ssr->t0[2].time&&fabs(t3)<MAXAGESSR_HRCLK) {
dclk+=ssr->hrclk;
}
if (norm(deph,3)>MAXECORSSR||fabs(dclk)>MAXCCORSSR) {
trace(3,"invalid ssr correction: %s deph=%.1f dclk=%.1f\n",
time_str(time,0),norm(deph,3),dclk);
*svh=-1;
return 0;
}
/* satellite postion and clock by broadcast ephemeris */
if (!ephpos(time,teph,sat,nav,ssr->iode,rs,dts,var,svh)) return 0;
/* satellite clock for gps, galileo and qzss */
sys=satsys(sat,NULL);
if (sys==SYS_GPS||sys==SYS_GAL||sys==SYS_QZS||sys==SYS_CMP) {
if (!(eph=seleph(teph,sat,ssr->iode,nav))) return 0;
/* satellite clock by clock parameters */
tk=timediff(time,eph->toc);
dts[0]=eph->f0+eph->f1*tk+eph->f2*tk*tk;
dts[1]=eph->f1+2.0*eph->f2*tk;
/* relativity correction */
dts[0]-=2.0*dot(rs,rs+3,3)/CLIGHT/CLIGHT;
}
/* radial-along-cross directions in ecef */
if (!normv3(rs+3,ea)) return 0;
cross3(rs,rs+3,rc);
if (!normv3(rc,ec)) {
*svh=-1;
return 0;
}
cross3(ea,ec,er);
/* satellite antenna offset correction */
if (opt) {
satantoff(time,rs,sat,nav,dant);
}
for (i=0;i<3;i++) {
rs[i]+=-(er[i]*deph[0]+ea[i]*deph[1]+ec[i]*deph[2])+dant[i];
}
/* t_corr = t_sv - (dts(brdc) + dclk(ssr) / CLIGHT) (ref [10] eq.3.12-7) */
dts[0]+=dclk/CLIGHT;
/* variance by ssr ura */
*var=var_urassr(ssr->ura);
trace(5,"satpos_ssr: %s sat=%2d deph=%6.3f %6.3f %6.3f er=%6.3f %6.3f %6.3f dclk=%6.3f var=%6.3f\n",
time_str(time,2),sat,deph[0],deph[1],deph[2],er[0],er[1],er[2],dclk,*var);
return 1;
}