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preceph.c
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preceph.c
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/*------------------------------------------------------------------------------
* preceph.c : precise ephemeris and clock functions
*
* Copyright (C) 2007-2020 by T.TAKASU, All rights reserved.
*
* references :
* [1] S.Hilla, The Extended Standard Product 3 Orbit Format (SP3-c),
* 12 February, 2007
* [2] J.Ray, W.Gurtner, RINEX Extensions to Handle Clock Information,
* 27 August, 1998
* [3] D.D.McCarthy, IERS Technical Note 21, IERS Conventions 1996, July 1996
* [4] D.A.Vallado, Fundamentals of Astrodynamics and Applications 2nd ed,
* Space Technology Library, 2004
* [5] S.Hilla, The Extended Standard Product 3 Orbit Format (SP3-d),
* February 21, 2016
*
* version : $Revision: 1.1 $ $Date: 2008/07/17 21:48:06 $
* history : 2009/01/18 1.0 new
* 2009/01/31 1.1 fix bug on numerical error to read sp3a ephemeris
* 2009/05/15 1.2 support glonass,galileo,qzs
* 2009/12/11 1.3 support wild-card expansion of file path
* 2010/07/21 1.4 added api:
* eci2ecef(),sunmoonpos(),peph2pos(),satantoff(),
* readdcb()
* changed api:
* readsp3()
* deleted api:
* eph2posp()
* 2010/09/09 1.5 fix problem when precise clock outage
* 2011/01/23 1.6 support qzss satellite code
* 2011/09/12 1.7 fix problem on precise clock outage
* move sunmmonpos() to rtkcmn.c
* 2011/12/01 1.8 modify api readsp3()
* precede later ephemeris if ephemeris is NULL
* move eci2ecef() to rtkcmn.c
* 2013/05/08 1.9 fix bug on computing std-dev of precise clocks
* 2013/11/20 1.10 modify option for api readsp3()
* 2014/04/03 1.11 accept extenstion including sp3,eph,SP3,EPH
* 2014/05/23 1.12 add function to read sp3 velocity records
* change api: satantoff()
* 2014/08/31 1.13 add member cov and vco in peph_t sturct
* 2014/10/13 1.14 fix bug on clock error variance in peph2pos()
* 2015/05/10 1.15 add api readfcb()
* modify api readdcb()
* 2017/04/11 1.16 fix bug on antenna offset correction in peph2pos()
* 2020/11/30 1.17 support SP3-d [5] to accept more than 85 satellites
* support NavIC/IRNSS in API peph2pos()
* LC defined GPS/QZS L1-L2, GLO G1-G2, GAL E1-E5b,
* BDS B1I-B2I and IRN L5-S for API satantoff()
* fix bug on reading SP3 file extension
*-----------------------------------------------------------------------------*/
#include "rtklib.h"
#define SQR(x) ((x)*(x))
#define NMAX 10 /* order of polynomial interpolation */
#define MAXDTE 900.0 /* max time difference to ephem time (s) */
#define EXTERR_CLK 1E-3 /* extrapolation error for clock (m/s) */
#define EXTERR_EPH 5E-7 /* extrapolation error for ephem (m/s^2) */
#define MAX_BIAS_SYS 4 /* # of constellations supported */
/* table to translate code to code bias table index */
static int8_t code_bias_ix[MAX_BIAS_SYS][MAXCODE];
/* initialize code bias lookup table -------------------------------------------
* -1 = code not supported
* 0 = reference code (0 bias)
* 1-3 = table index for code
* ----------------------------------------------------------------------------*/
static void init_bias_ix(void) {
int i,j;
for (i=0;i<MAX_BIAS_SYS;i++) for (j=0;j<MAXCODE;j++)
code_bias_ix[i][j]=-1;
/* GPS */
code_bias_ix[0][CODE_L1W]=0;
code_bias_ix[0][CODE_L1C]=1;
code_bias_ix[0][CODE_L1L]=2;
code_bias_ix[0][CODE_L1X]=3;
code_bias_ix[0][CODE_L2W]=0;
code_bias_ix[0][CODE_L2L]=1;
code_bias_ix[0][CODE_L2S]=2;
code_bias_ix[0][CODE_L2X]=3;
/* GLONASS */
code_bias_ix[1][CODE_L1P]=0;
code_bias_ix[1][CODE_L1C]=1;
code_bias_ix[1][CODE_L2P]=0;
code_bias_ix[1][CODE_L2C]=1;
/* Galileo */
code_bias_ix[2][CODE_L1C]=0;
code_bias_ix[2][CODE_L1X]=1;
code_bias_ix[2][CODE_L5Q]=0;
code_bias_ix[2][CODE_L5I]=1;
code_bias_ix[2][CODE_L5X]=2;
/* Beidou */
code_bias_ix[3][CODE_L2I]=0;
code_bias_ix[3][CODE_L6I]=0;
}
/* satellite code to satellite system ----------------------------------------*/
static int code2sys(char code)
{
if (code=='G'||code==' ') return SYS_GPS;
if (code=='R') return SYS_GLO;
if (code=='E') return SYS_GAL; /* SP3-d */
if (code=='J') return SYS_QZS; /* SP3-d */
if (code=='C') return SYS_CMP; /* SP3-d */
if (code=='I') return SYS_IRN; /* SP3-d */
if (code=='L') return SYS_LEO; /* SP3-d */
return SYS_NONE;
}
/* read SP3 header -----------------------------------------------------------*/
static int readsp3h(FILE *fp, gtime_t *time, char *type, int *sats,
double *bfact, char *tsys)
{
int i=0,j,k=0,ns=0,nl=5,sys,prn;
char buff[1024];
trace(3,"readsp3h:\n");
/* TODO: Still using b33 code due to issues with b34 */
while (fgets(buff,sizeof(buff),fp)) {
if (buff[0]=='#'&&(buff[1]=='c'||buff[1]=='d')) {
*type=buff[2];
if (str2time(buff,3,28,time)) return 0;
}
else if (buff[0]=='+'&&buff[1]==' ') {
if (i==2) {
ns=(int)str2num(buff,3,3);
if (ns>85) nl=ns/17+(ns%17!=0);
}
for (j=0;j<17&&k<ns;j++) {
sys=code2sys(buff[9+3*j]);
prn=(int)str2num(buff,10+3*j,2);
if (k<MAXSAT) sats[k++]=satno(sys,prn);
}
}
else if (i==2*nl+2) {/* %c */
memcpy(tsys,buff+9,3); tsys[3]='\0';
}
else if (i==2*nl+4) {/* %f */
bfact[0]=str2num(buff, 3,10);
bfact[1]=str2num(buff,14,12);
}
else if (i==2*nl+11){
break; /* at end of header */
}
i=i+1; /* line counter */
}
return ns;
}
/* add precise ephemeris -----------------------------------------------------*/
static int addpeph(nav_t *nav, peph_t *peph)
{
peph_t *nav_peph;
if (nav->ne>=nav->nemax) {
nav->nemax+=256;
if (!(nav_peph=(peph_t *)realloc(nav->peph,sizeof(peph_t)*nav->nemax))) {
trace(1,"readsp3b malloc error n=%d\n",nav->nemax);
free(nav->peph); nav->peph=NULL; nav->ne=nav->nemax=0;
return 0;
}
nav->peph=nav_peph;
}
nav->peph[nav->ne++]=*peph;
return 1;
}
/* read SP3 body -------------------------------------------------------------*/
static void readsp3b(FILE *fp, char type, int *sats, int ns, double *bfact,
char *tsys, int index, int opt, nav_t *nav)
{
peph_t peph;
gtime_t time;
double val,std,base;
int i,j,sat,sys,prn,n=ns*(type=='P'?1:2),pred_o,pred_c,v;
char buff[1024];
trace(3,"readsp3b: type=%c ns=%d index=%d opt=%d\n",type,ns,index,opt);
while (fgets(buff,sizeof(buff),fp)) {
if (!strncmp(buff,"EOF",3)) break;
if (buff[0]!='*'||str2time(buff,3,28,&time)) {
trace(2,"sp3 invalid epoch %31.31s\n",buff);
continue;
}
if (!strcmp(tsys,"UTC")) time=utc2gpst(time); /* utc->gpst */
peph.time =time;
peph.index=index;
for (i=0;i<MAXSAT;i++) {
for (j=0;j<4;j++) {
peph.pos[i][j]=0.0;
peph.std[i][j]=0.0f;
peph.vel[i][j]=0.0;
peph.vst[i][j]=0.0f;
}
for (j=0;j<3;j++) {
peph.cov[i][j]=0.0f;
peph.vco[i][j]=0.0f;
}
}
for (i=pred_o=pred_c=v=0;i<n&&fgets(buff,sizeof(buff),fp);i++) {
if (strlen(buff)<4||(buff[0]!='P'&&buff[0]!='V')) continue;
sys=buff[1]==' '?SYS_GPS:code2sys(buff[1]);
prn=(int)str2num(buff,2,2);
if (sys==SYS_SBS) prn+=100;
else if (sys==SYS_QZS) prn+=192; /* extension to sp3-c */
if (!(sat=satno(sys,prn))) continue;
if (buff[0]=='P') {
pred_c=strlen(buff)>=76&&buff[75]=='P';
pred_o=strlen(buff)>=80&&buff[79]=='P';
}
for (j=0;j<4;j++) {
/* read option for predicted value */
if (j< 3&&(opt&1)&& pred_o) continue;
if (j< 3&&(opt&2)&&!pred_o) continue;
if (j==3&&(opt&1)&& pred_c) continue;
if (j==3&&(opt&2)&&!pred_c) continue;
val=str2num(buff, 4+j*14,14);
std=str2num(buff,61+j* 3,j<3?2:3);
if (buff[0]=='P') { /* position */
if (val!=0.0&&fabs(val-999999.999999)>=1E-6) {
peph.pos[sat-1][j]=val*(j<3?1000.0:1E-6);
v=1; /* valid epoch */
}
if ((base=bfact[j<3?0:1])>0.0&&std>0.0) {
peph.std[sat-1][j]=(float)(pow(base,std)*(j<3?1E-3:1E-12));
}
}
else if (v) { /* velocity */
if (val!=0.0&&fabs(val-999999.999999)>=1E-6) {
peph.vel[sat-1][j]=val*(j<3?0.1:1E-10);
}
if ((base=bfact[j<3?0:1])>0.0&&std>0.0) {
peph.vst[sat-1][j]=(float)(pow(base,std)*(j<3?1E-7:1E-16));
}
}
}
}
if (v) {
if (!addpeph(nav,&peph)) return;
}
}
}
/* compare precise ephemeris -------------------------------------------------*/
static int cmppeph(const void *p1, const void *p2)
{
peph_t *q1=(peph_t *)p1,*q2=(peph_t *)p2;
double tt=timediff(q1->time,q2->time);
return tt<-1E-9?-1:(tt>1E-9?1:q1->index-q2->index);
}
/* combine precise ephemeris -------------------------------------------------*/
static void combpeph(nav_t *nav, int opt)
{
int i,j,k,m;
trace(3,"combpeph: ne=%d\n",nav->ne);
qsort(nav->peph,nav->ne,sizeof(peph_t),cmppeph);
if (opt&4) return;
for (i=0,j=1;j<nav->ne;j++) {
if (fabs(timediff(nav->peph[i].time,nav->peph[j].time))<1E-9) {
for (k=0;k<MAXSAT;k++) {
if (norm(nav->peph[j].pos[k],4)<=0.0) continue;
for (m=0;m<4;m++) nav->peph[i].pos[k][m]=nav->peph[j].pos[k][m];
for (m=0;m<4;m++) nav->peph[i].std[k][m]=nav->peph[j].std[k][m];
for (m=0;m<4;m++) nav->peph[i].vel[k][m]=nav->peph[j].vel[k][m];
for (m=0;m<4;m++) nav->peph[i].vst[k][m]=nav->peph[j].vst[k][m];
}
}
else if (++i<j) nav->peph[i]=nav->peph[j];
}
nav->ne=i+1;
trace(4,"combpeph: ne=%d\n",nav->ne);
}
/* read sp3 precise ephemeris file ---------------------------------------------
* read sp3 precise ephemeris/clock files and set them to navigation data
* args : char *file I sp3-c precise ephemeris file
* (wind-card * is expanded)
* nav_t *nav IO navigation data
* int opt I options (1: only observed + 2: only predicted +
* 4: not combined)
* return : none
* notes : see ref [1]
* precise ephemeris is appended and combined
* nav->peph and nav->ne must by properly initialized before calling the
* function
* only files with extensions of .sp3, .SP3, .eph* and .EPH* are read
*-----------------------------------------------------------------------------*/
extern void readsp3(const char *file, nav_t *nav, int opt)
{
FILE *fp;
gtime_t time={0};
double bfact[2]={0};
int i,j,n,ns,sats[MAXSAT]={0};
char *efiles[MAXEXFILE],*ext,type=' ',tsys[4]="";
trace(3,"readpephs: file=%s\n",file);
for (i=0;i<MAXEXFILE;i++) {
if (!(efiles[i]=(char *)malloc(1024))) {
for (i--;i>=0;i--) free(efiles[i]);
return;
}
}
/* expand wild card in file path */
n=expath(file,efiles,MAXEXFILE);
for (i=j=0;i<n;i++) {
if (!(ext=strrchr(efiles[i],'.'))) continue;
if (!strstr(ext,".sp3")&&!strstr(ext,".SP3")&&
!strstr(ext,".eph")&&!strstr(ext,".EPH")) continue;
if (!(fp=fopen(efiles[i],"r"))) {
trace(2,"sp3 file open error %s\n",efiles[i]);
continue;
}
/* read sp3 header */
ns=readsp3h(fp,&time,&type,sats,bfact,tsys);
/* read sp3 body */
readsp3b(fp,type,sats,ns,bfact,tsys,j++,opt,nav);
fclose(fp);
}
for (i=0;i<MAXEXFILE;i++) free(efiles[i]);
/* combine precise ephemeris */
if (nav->ne>0) combpeph(nav,opt);
}
/* read satellite antenna parameters -------------------------------------------
* read satellite antenna parameters
* args : char *file I antenna parameter file
* gtime_t time I time
* nav_t *nav IO navigation data
* return : status (1:ok,0:error)
* notes : only support antex format for the antenna parameter file
*-----------------------------------------------------------------------------*/
extern int readsap(const char *file, gtime_t time, nav_t *nav)
{
pcvs_t pcvs={0};
pcv_t pcv0={0},*pcv;
int i;
trace(3,"readsap : file=%s time=%s\n",file,time_str(time,0));
if (!readpcv(file,&pcvs)) return 0;
for (i=0;i<MAXSAT;i++) {
pcv=searchpcv(i+1,"",time,&pcvs);
nav->pcvs[i]=pcv?*pcv:pcv0;
}
free(pcvs.pcv);
return 1;
}
/* read DCB parameters from DCB file -------------------------------------------
* - supports satellite and receiver biases
*-----------------------------------------------------------------------------*/
static int readdcbf(const char *file, nav_t *nav, const sta_t *sta)
{
FILE *fp;
double cbias;
char buff[256],str1[32],str2[32]="";
int i,j,sat,type=0;
trace(3,"readdcbf: file=%s\n",file);
if (!(fp=fopen(file,"r"))) {
trace(2,"dcb parameters file open error: %s\n",file);
return 0;
}
while (fgets(buff,sizeof(buff),fp)) {
if (strstr(buff,"DIFFERENTIAL (P1-C1) CODE BIASES")) type=1;
else if (strstr(buff,"DIFFERENTIAL (P2-C2) CODE BIASES")) type=2;
str2[0]='\0';
if (!type||sscanf(buff,"%31s %31s",str1,str2)<1) continue;
if ((cbias=str2num(buff,26,9))==0.0) continue;
if (sta&&(!strcmp(str1,"G")||!strcmp(str1,"R"))) { /* receiver DCB */
for (i=0;i<MAXRCV;i++) {
if (!strcmp(sta[i].name,str2)) break;
}
if (i<MAXRCV) {
j=!strcmp(str1,"G")?0:1;
nav->rbias[i][j][type-1]=cbias*1E-9*CLIGHT; /* ns -> m */
}
}
else if ((sat=satid2no(str1))) { /* satellite dcb */
nav->cbias[sat-1][type-1][0]=cbias*1E-9*CLIGHT; /* ns -> m */
}
}
fclose(fp);
return 1;
}
/* satellite system to index */
static int sys2ix(int sys)
{
switch (sys) {
case SYS_GPS: return 0;
case SYS_SBS: return 0;
case SYS_GLO: return 1;
case SYS_GAL: return 2;
case SYS_CMP: return 3;
case SYS_QZS: return 4;
case SYS_IRN: return 5;
}
return 0;
}
/* translate satellite system and code to code bias table index ----------------
* -1 = code not supported
* 0 = reference code (0 bias)
* 1-3 = table index for code
* ----------------------------------------------------------------------------*/
extern int code2bias_ix(int sys, int code) {
int sys_ix;
sys_ix=sys2ix(sys);
if (sys_ix<MAX_BIAS_SYS)
return code_bias_ix[sys_ix][code];
else
return 0;
}
/* read DCB parameters from BIA or BSX file ------------------------------------
* - supports satellite code biases only
*-----------------------------------------------------------------------------*/
static int readbiaf(const char *file, nav_t *nav)
{
FILE *fp;
double cbias;
char buff[256],bias[6]="",svn[6]="",prn[6]="",obs1[6]="",obs2[6];
int i,sat,freq,code1,code2,bias_ix1,bias_ix2,sys;
trace(3,"readbiaf: file=%s\n",file);
if (!(fp=fopen(file,"r"))) {
trace(2,"dcb parameters file open error: %s\n",file);
return 0;
}
while (fgets(buff,sizeof(buff),fp)) {
if (sscanf(buff,"%4s %5s %4s %4s %4s",bias,svn,prn,obs1,obs2)<5) continue;
if (obs1[0]!='C') continue; /* skip phase biases for now */
if ((cbias=str2num(buff,70,21))==0.0) continue;
sat=satid2no(prn);
sys=satsys(sat,NULL);
/* other code biases are L1/L2, Galileo is L1/L5 */
if (obs1[1]=='1')
freq=0;
else if ((sys!=SYS_GAL&&obs1[1]=='2')||(sys==SYS_GAL&&obs1[1]=='5'))
freq=1;
else continue;
if (!(code1=obs2code(&obs1[1]))) continue; /* skip if code not valid */
bias_ix1=code2bias_ix(sys,code1);
if (strcmp(bias,"OSB")==0) {
/* observed signal bias */
if (bias_ix1==0) { /* this is ref code */
for (i=0;i<MAX_CODE_BIASES;i++)
/* adjust all other codes by ref code bias */
nav->cbias[sat-1][freq][i]+=cbias*1E-9*CLIGHT; /* ns -> m */
} else {
nav->cbias[sat-1][freq][bias_ix1-1]-=cbias*1E-9*CLIGHT; /* ns -> m */
}
}
else if (strcmp(bias,"DSB")==0) {
/* differential signal bias */
if (obs1[1]!=obs2[1]) continue; /* skip biases between freqs for now */
if (!(code2=obs2code(&obs2[1]))) continue; /* skip if code not valid */
bias_ix2=code2bias_ix(sys,code2);
if (bias_ix1==0) /* this is ref code */
nav->cbias[sat-1][freq][bias_ix2-1]=cbias*1E-9*CLIGHT; /* ns -> m */
else if (bias_ix2==0) /* this is ref code */
nav->cbias[sat-1][freq][bias_ix1-1]=-cbias*1E-9*CLIGHT; /* ns -> m */
}
}
fclose(fp);
return 1;
}
/* read DCB parameters ---------------------------------------------------------
* read differential code bias (DCB) parameters
* args : char *file I DCB parameters file (wild-card * expanded)
* nav_t *nav IO navigation data
* sta_t *sta I station info data to import receiver DCB
* (NULL: no use)
* return : status (1:ok,0:error)
* notes : supports DCB, BIA, and BSX file formats
: currently only support P1-P2, P1-C1 bias in DCB file
: currently only supports satellite biases in BIA/BSX files
*-----------------------------------------------------------------------------*/
extern int readdcb(const char *file, nav_t *nav, const sta_t *sta)
{
int i,j,k,n,dcb_ok=0;
char *efiles[MAXEXFILE]={0};
trace(3,"readdcb : file=%s\n",file);
init_bias_ix(); /* init translation table from code to table column */
for (i=0;i<MAXSAT;i++) for (j=0;j<MAX_CODE_BIAS_FREQS;j++) for (k=0;k<MAX_CODE_BIASES;k++) {
nav->cbias[i][j][k]=0.0;
}
for (i=0;i<MAXEXFILE;i++) {
if (!(efiles[i]=(char *)malloc(1024))) {
for (i--;i>=0;i--) free(efiles[i]);
return 0;
}
}
n=expath(file,efiles,MAXEXFILE);
for (i=0;i<n;i++) {
if (strstr(efiles[i],".BIA")||strstr(efiles[i],".bia")||
strstr(efiles[i],".BSX")||strstr(efiles[i],".bsx"))
dcb_ok=readbiaf(efiles[i],nav);
else if (strstr(efiles[i],".DCB")||strstr(efiles[i],".dcb"))
dcb_ok=readdcbf(efiles[i],nav,sta);
}
for (i=0;i<MAXEXFILE;i++) free(efiles[i]);
return dcb_ok;
}
/* polynomial interpolation by Neville's algorithm ---------------------------*/
static double interppol(const double *x, double *y, int n)
{
int i,j;
for (j=1;j<n;j++) {
for (i=0;i<n-j;i++) {
y[i]=(x[i+j]*y[i]-x[i]*y[i+1])/(x[i+j]-x[i]);
}
}
return y[0];
}
/* satellite position by precise ephemeris -----------------------------------*/
static int pephpos(gtime_t time, int sat, const nav_t *nav, double *rs,
double *dts, double *vare, double *varc)
{
double t[NMAX+1],p[3][NMAX+1],c[2],*pos,std=0.0,s[3],sinl,cosl;
int i,j,k,index;
trace(4,"pephpos : time=%s sat=%2d\n",time_str(time,3),sat);
rs[0]=rs[1]=rs[2]=dts[0]=0.0;
if (nav->ne<NMAX+1||
timediff(time,nav->peph[0].time)<-MAXDTE||
timediff(time,nav->peph[nav->ne-1].time)>MAXDTE) {
trace(3,"no prec ephem %s sat=%2d\n",time_str(time,0),sat);
return 0;
}
/* binary search */
for (i=0,j=nav->ne-1;i<j;) {
k=(i+j)/2;
if (timediff(nav->peph[k].time,time)<0.0) i=k+1; else j=k;
}
index=i<=0?0:i-1;
/* polynomial interpolation for orbit */
i=index-(NMAX+1)/2;
if (i<0) i=0; else if (i+NMAX>=nav->ne) i=nav->ne-NMAX-1;
for (j=0;j<=NMAX;j++) {
t[j]=timediff(nav->peph[i+j].time,time);
if (norm(nav->peph[i+j].pos[sat-1],3)<=0.0) {
trace(3,"prec ephem outage %s sat=%2d\n",time_str(time,0),sat);
return 0;
}
}
for (j=0;j<=NMAX;j++) {
pos=nav->peph[i+j].pos[sat-1];
/* correction for earth rotation ver.2.4.0 */
sinl=sin(OMGE*t[j]);
cosl=cos(OMGE*t[j]);
p[0][j]=cosl*pos[0]-sinl*pos[1];
p[1][j]=sinl*pos[0]+cosl*pos[1];
p[2][j]=pos[2];
}
for (i=0;i<3;i++) {
rs[i]=interppol(t,p[i],NMAX+1);
}
if (vare) {
for (i=0;i<3;i++) s[i]=nav->peph[index].std[sat-1][i];
std=norm(s,3);
/* extrapolation error for orbit */
if (t[0 ]>0.0) std+=EXTERR_EPH*SQR(t[0 ])/2.0;
else if (t[NMAX]<0.0) std+=EXTERR_EPH*SQR(t[NMAX])/2.0;
*vare=SQR(std);
}
/* linear interpolation for clock */
t[0]=timediff(time,nav->peph[index ].time);
t[1]=timediff(time,nav->peph[index+1].time);
c[0]=nav->peph[index ].pos[sat-1][3];
c[1]=nav->peph[index+1].pos[sat-1][3];
if (t[0]<=0.0) {
if ((dts[0]=c[0])!=0.0) {
std=nav->peph[index].std[sat-1][3]*CLIGHT-EXTERR_CLK*t[0];
}
}
else if (t[1]>=0.0) {
if ((dts[0]=c[1])!=0.0) {
std=nav->peph[index+1].std[sat-1][3]*CLIGHT+EXTERR_CLK*t[1];
}
}
else if (c[0]!=0.0&&c[1]!=0.0) {
dts[0]=(c[1]*t[0]-c[0]*t[1])/(t[0]-t[1]);
i=t[0]<-t[1]?0:1;
std=nav->peph[index+i].std[sat-1][3]+EXTERR_CLK*fabs(t[i]);
}
else {
dts[0]=0.0;
}
if (varc) *varc=SQR(std);
return 1;
}
/* satellite clock by precise clock ------------------------------------------*/
static int pephclk(gtime_t time, int sat, const nav_t *nav, double *dts,
double *varc)
{
double t[2],c[2],std;
int i,j,k,index;
trace(4,"pephclk : time=%s sat=%2d\n",time_str(time,3),sat);
if (nav->nc<2||
timediff(time,nav->pclk[0].time)<-MAXDTE||
timediff(time,nav->pclk[nav->nc-1].time)>MAXDTE) {
trace(3,"no prec clock %s sat=%2d\n",time_str(time,0),sat);
return 1;
}
/* binary search */
for (i=0,j=nav->nc-1;i<j;) {
k=(i+j)/2;
if (timediff(nav->pclk[k].time,time)<0.0) i=k+1; else j=k;
}
index=i<=0?0:i-1;
/* linear interpolation for clock */
t[0]=timediff(time,nav->pclk[index ].time);
t[1]=timediff(time,nav->pclk[index+1].time);
c[0]=nav->pclk[index ].clk[sat-1][0];
c[1]=nav->pclk[index+1].clk[sat-1][0];
if (t[0]<=0.0) {
if ((dts[0]=c[0])==0.0) return 0;
std=nav->pclk[index].std[sat-1][0]*CLIGHT-EXTERR_CLK*t[0];
}
else if (t[1]>=0.0) {
if ((dts[0]=c[1])==0.0) return 0;
std=nav->pclk[index+1].std[sat-1][0]*CLIGHT+EXTERR_CLK*t[1];
}
else if (c[0]!=0.0&&c[1]!=0.0) {
dts[0]=(c[1]*t[0]-c[0]*t[1])/(t[0]-t[1]);
i=t[0]<-t[1]?0:1;
std=nav->pclk[index+i].std[sat-1][0]*CLIGHT+EXTERR_CLK*fabs(t[i]);
}
else {
trace(3,"prec clock outage %s sat=%2d\n",time_str(time,0),sat);
return 0;
}
if (varc) *varc=SQR(std);
return 1;
}
/* satellite antenna phase center offset ---------------------------------------
* compute satellite antenna phase center offset in ecef
* args : gtime_t time I time (gpst)
* double *rs I satellite position and velocity (ecef)
* {x,y,z,vx,vy,vz} (m|m/s)
* int sat I satellite number
* nav_t *nav I navigation data
* double *dant O satellite antenna phase center offset (ecef)
* {dx,dy,dz} (m) (iono-free LC value)
* return : none
* notes : iono-free LC frequencies defined as follows:
* GPS/QZSS : L1-L2
* GLONASS : G1-G2
* Galileo : E1-E5b
* BDS : B1I-B2I
* NavIC : L5-S
*-----------------------------------------------------------------------------*/
extern void satantoff(gtime_t time, const double *rs, int sat, const nav_t *nav,
double *dant)
{
const pcv_t *pcv=nav->pcvs+sat-1;
double ex[3],ey[3],ez[3],es[3],r[3],rsun[3],gmst,erpv[5]={0},freq[2];
double C1,C2,dant1,dant2;
int i,sys;
trace(4,"satantoff: time=%s sat=%2d\n",time_str(time,3),sat);
dant[0]=dant[1]=dant[2]=0.0;
/* sun position in ecef */
sunmoonpos(gpst2utc(time),erpv,rsun,NULL,&gmst);
/* unit vectors of satellite fixed coordinates */
for (i=0;i<3;i++) r[i]=-rs[i];
if (!normv3(r,ez)) return;
for (i=0;i<3;i++) r[i]=rsun[i]-rs[i];
if (!normv3(r,es)) return;
cross3(ez,es,r);
if (!normv3(r,ey)) return;
cross3(ey,ez,ex);
/* iono-free LC coefficients */
sys=satsys(sat,NULL);
if (sys==SYS_GPS||sys==SYS_QZS) { /* L1-L2 */
freq[0]=FREQL1;
freq[1]=FREQL2;
}
else if (sys==SYS_GLO) { /* G1-G2 */
freq[0]=sat2freq(sat,CODE_L1C,nav);
freq[1]=sat2freq(sat,CODE_L2C,nav);
}
else if (sys==SYS_GAL) { /* E1-E5b */
freq[0]=FREQL1;
freq[1]=FREQE5b;
}
else if (sys==SYS_CMP) { /* B1I-B2I */
freq[0]=FREQ1_CMP;
freq[1]=FREQ2_CMP;
}
else if (sys==SYS_IRN) { /* L5-S */
freq[0]=FREQL5;
freq[1]=FREQs;
}
else return;
C1= SQR(freq[0])/(SQR(freq[0])-SQR(freq[1]));
C2=-SQR(freq[1])/(SQR(freq[0])-SQR(freq[1]));
/* iono-free LC */
for (i=0;i<3;i++) {
dant1=pcv->off[0][0]*ex[i]+pcv->off[0][1]*ey[i]+pcv->off[0][2]*ez[i];
dant2=pcv->off[1][0]*ex[i]+pcv->off[1][1]*ey[i]+pcv->off[1][2]*ez[i];
dant[i]=C1*dant1+C2*dant2;
}
}
/* 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 position 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)
{
gtime_t time_tt;
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_tt=timeadd(time,tt);
if (!pephpos(time_tt,sat,nav,rst,dtst,NULL,NULL)||
!pephclk(time_tt,sat,nav,dtst,NULL)) return 0;
/* satellite antenna offset correction */
if (opt) {
satantoff(time,rss,sat,nav,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*dot3(rs,rs+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;
}