int getLookYaw(GEOLOCATE_REC *g,double range,double dop, /* Inputs.*/
double *out_look,double *out_yaw)/* Outputs, in radians.*/
{
int iterations=0,err=0,max_iter=10000;
double yaw=0,deltaAz;
double look=0;
double dopGuess,dopDotGuess,deltaDop,prevDeltaDop=-9999999;
vector target,vRel;
while (1)
{
double relativeVelocity;
//if (iterations>10) printf("GetLoc: Iteration %i, doppler=%f, yaw=%20.18f, look=%20.18f.\n",iterations,dopGuess,yaw*180/M_PI,look*180/M_PI);
err=getLook(g,range,yaw,&look);
if (err) break;
getDoppler(g,look,yaw,&dopGuess,&dopDotGuess,&target,&vRel);
deltaDop=dop-dopGuess;
relativeVelocity=vecMagnitude(vRel);
deltaAz=deltaDop*(g->lambda/(2*relativeVelocity));
// handle the zero doppler case -- without this, we will
// sometimes flip back&forth accross zero doppler, until max_iter
if (fabs(deltaDop+prevDeltaDop)<.000001) deltaAz/=2.;
if (fabs(deltaAz*range)<0.1)/*Require decimeter convergence*/
break;
yaw+=deltaAz;
if (++iterations>max_iter) { /* Failed to converge */
err=1; break;
}
prevDeltaDop=deltaDop;
}
*out_look=look;
*out_yaw=yaw;
return err;
}
int getLoc(GEOLOCATE_REC *g,double range,double dop, /* Inputs.*/
double *latitude,double *phi,double *earthRadius) /*Outputs.*/
{
int err;
double yaw=0,look=0;
vector target;
err = getLookYaw(g,range,dop,&look,&yaw);
if (err) return err;
getDoppler(g,look,yaw,NULL,NULL,&target,NULL);
cart2sph(target,earthRadius,latitude,phi);
return 0;
}
/*
* Compute and manipulate range/velocity/antenna vectors
*/
void Plan13::rangevec(void)
{
if (DEBUG) {Serial.println("Start rangevec()");}
/* Range vector = sat vector - observer vector */
Rx = Sx - Ox;
Ry = Sy - Oy;
Rz = Sz - Oz;
R = sqrt(Rx * Rx + Ry * Ry + Rz * Rz); /* Range Magnitute */
/* Normalize range vector */
Rx = Rx / R;
Ry = Ry / R;
Rz = Rz / R;
U = Rx * Ux + Ry * Uy + Rz * Uz;
E = Rx * Ex + Ry * Ey;
N = Rx * Nx + Ry * Ny + Rz * Nz;
AZ = deg(FNatn(E, N));
EL = deg(asin(U));
/* Solve antenna vector along unit range vector, -r.a = cos(SQ) */
/* SQ = deg(acos(-(Ax * Rx + Ay * Ry + Az * Rz)));
*/
/* Calculate sub-satellite Lat/Lon */
SLON = deg(FNatn(Sy, Sx)); /* Lon, + East */
SLAT = deg(asin(Sz / RS)); /* Lat, + North */
/* Resolve Sat-Obs velocity vector along unit range vector. (VOz = 0) */
RR = (Vx - VOx) * Rx + (Vy - VOy) * Ry + Vz * Rz; /* Range rate, km/sec */
//FR = rxFrequency * (1 - RR / 299792);
dopplerFactor = RR / 299792.0;
int rxDoppler = getDoppler(rxFrequencyLong);
int txDoppler = getDoppler(txFrequencyLong);
rxOutLong = rxFrequencyLong - rxDoppler;
txOutLong = txFrequencyLong + txDoppler;
if (DEBUG) {Serial.println("End rangevec()");}
}
void prep_specan_file(int nLooks,int quality,double aspect,
struct ARDOP_PARAMS *g,meta_parameters *meta)
{
getRec *inFile;
FILE *outFile;
int outLines,outSamples/*,x*/;
/*char command[1024];*/
int i;
specan_struct rng={1.0/RFS,
RSLOPE,
RCEN,
RBW,
RLEN_INIT};
specan_struct az={1.0/AFS,
ASLOPE,
ACEN,
ABW,
ALEN_INIT};
/*Set quality: longer FFT's -> bigger
image, better quality.*/
for (i=0;i<quality;i++)
{
rng.fftLen*=2;
az.fftLen*=2;
}
rng.fftLen=(int)(rng.fftLen*aspect);
/*Open files.*/
if (!quietflag) printf("Opening input files...\n");
inFile=fillOutGetRec(g->in1);
outFile=fopenImage(g->out,"wb");
/*Init. Range Variables*/
if (!quietflag) printf("Init SPECAN\n");
rng.iSamp=1.0/g->fs;/*Sample size, range (s)= 1.0/sample freqency (Hz)*/
rng.chirpSlope=g->slope;/*Range chirp slope (Hz/Sec)*/
specan_init(&rng);
/*Init. Azimuth Variables*/
if (!quietflag) printf("Estimate Doppler\n");
az.iSamp=1.0/g->prf;/*Sample size, azimuth (s)=1.0/sample freqency (Hz)*/
if (meta->stVec==NULL) {
fprintf(stderr, "Can only quicklook scenes with state vectors!\n");
exit(1);}
else { /*Find doppler rate (Hz/sec) <=> azimuth chirp slope*/
double dopRate,yaw=0.0;
GEOLOCATE_REC *g=init_geolocate_meta(&meta->stVec->vecs[0].vec,meta);
double look;
int ret;
ret=getLook(g,meta->geo->slantFirst,yaw,&look);
assert(ret==0);
getDoppler(g,look,yaw,NULL,&dopRate,NULL,NULL);
az.chirpSlope=dopRate;
free_geolocate(g);
}
az.chirpCenter=g->fd*(1.0/az.iSamp);/*Convert doppler central freqency to Hz*/
/*For de-scalloping, compute the most powerful doppler freqency.*/
az.powerCenter=(1.0/az.iSamp)*
fftEstDop(inFile,inFile->nLines/2,1,az.fftLen);
if (!quietflag) printf("Doppler centroid at %.0f Hz, %.0f Hz/sec\n",az.chirpCenter,az.chirpSlope);
specan_init(&az);
if (!quietflag) printf("Efficiency: Range(%d): %.0f%% Azimuth(%d): %.0f%%\n",
rng.fftLen,100.0*rng.oNum/rng.fftLen,
az.fftLen,100.0*az.oNum/az.fftLen);
/*Process image.*/
specan_file(inFile,nLooks,outFile,&rng,&az,&outLines,&outSamples);
FCLOSE(outFile);
freeGetRec(inFile);
/*Create DDR for output file.*/
{
struct DDR ddr;/*Output DDR*/
c_intddr(&ddr);
ddr.dtype=DTYPE_FLOAT;
ddr.nbands=1;
ddr.nl=outLines;
ddr.ns=outSamples;
ddr.sample_inc=rng.oSamp/rng.iSamp;
ddr.line_inc=az.oSamp/az.iSamp;
c_putddr(g->out,&ddr);
}
/*Copy over metadata*/
if (meta->info)
sprintf(meta->info->processor,"ASF/QUICKLOOK/%.2f",VERSION);
meta_write(meta,g->out);
}
