RadarGroundMap.cpp

Go to the documentation of this file.

#include "RadarGroundMap.h"
#include "iTime.h"
#include "Latitude.h"
#include "Longitude.h"
#include "Target.h"

using namespace std;

namespace Isis {
  RadarGroundMap::RadarGroundMap(Camera *parent, Radar::LookDirection ldir,
                                 double waveLength) :
    CameraGroundMap(parent) {
    p_camera = parent;
    p_lookDirection = ldir;
    p_waveLength = waveLength;

    // Angular tolerance based on radii and
    // slant range (Focal length)
//    Distance radii[3];
//    p_camera->radii(radii);
//    p_tolerance = p_camera->FocalLength() / radii[2];
//    p_tolerance *= 180.0 / Isis::PI;
    p_tolerance = .0001;

    // Compute a default time tolerance to a 1/20 of a pixel
    double et1 = p_camera->Spice::cacheStartTime().Et();
    double et2 = p_camera->Spice::cacheEndTime().Et();
    p_timeTolerance = (et2 - et1) / p_camera->Lines() / 20.0;
  }

  bool RadarGroundMap::SetFocalPlane(const double ux, const double uy,
                                     double uz) {

    SpiceRotation *bodyFrame = p_camera->bodyRotation();
    SpicePosition *spaceCraft = p_camera->instrumentPosition();

    // Get spacecraft position and velocity to create a state vector
    std::vector<double> Ssc(6);
    // Load the state into Ssc
    vequ_c((SpiceDouble *) & (spaceCraft->Coordinate()[0]), &Ssc[0]);
    vequ_c((SpiceDouble *) & (spaceCraft->Velocity()[0]), &Ssc[3]);

    // Rotate state vector to body-fixed
    std::vector<double> bfSsc(6);
    bfSsc = bodyFrame->ReferenceVector(Ssc);

    // Extract body-fixed position and velocity
    std::vector<double> Vsc(3);
    std::vector<double> Xsc(3);
    vequ_c(&bfSsc[0], (SpiceDouble *) & (Xsc[0]));
    vequ_c(&bfSsc[3], (SpiceDouble *) & (Vsc[0]));

    // Compute intrack, crosstrack, and radial coordinate
    SpiceDouble i[3];
    vhat_c(&Vsc[0], i);

    SpiceDouble c[3];
    SpiceDouble dp;
    dp = vdot_c(&Xsc[0], i);
    SpiceDouble p[3], q[3];
    vscl_c(dp, i, p);
    vsub_c(&Xsc[0], p, q);
    vhat_c(q, c);

    SpiceDouble r[3];
    vcrss_c(i, c, r);

    // What is the initial guess for R
    Distance radii[3];
    p_camera->radii(radii);
    SpiceDouble R = radii[0].kilometers();

    SpiceDouble lat = DBL_MAX;
    SpiceDouble lon = DBL_MAX;

    double slantRangeSqr = (ux * p_rangeSigma) / 1000.;   // convert to meters, then km
    slantRangeSqr = slantRangeSqr * slantRangeSqr;
    SpiceDouble X[3];

    // The iteration code was moved to its own method so that it can be run multiple times
    // if necessary. The first iteration should suffice for those pixels that have shallow
    // slopes. For those pixels that lie on steep slopes (up to 2x the incidence angle), then
    // an additional iteration call is needed. In the future, we may need to add more calls
    // to the iteration method if the slope is greater than 2x the incidence angle. The
    // slope variable will need to be halved each time the iteration method is called until
    // a solution is found. So, for example, if we needed to call the iteration method a third
    // time, the slope variable would be set to .25.
    bool useSlopeEqn = false;
    double slope = .5;
    bool success = Iterate(R,slantRangeSqr,c,r,X,lat,lon,Xsc,useSlopeEqn,slope);

    if(!success) {
      R = radii[0].kilometers();
      useSlopeEqn = true;
      success = Iterate(R,slantRangeSqr,c,r,X,lat,lon,Xsc,useSlopeEqn,slope);
    }

    if(!success) return false;

    lat = lat * 180.0 / Isis::PI;
    lon = lon * 180.0 / Isis::PI;
    while(lon < 0.0) lon += 360.0;

    // Compute body fixed look direction
    std::vector<double> lookB;
    lookB.resize(3);
    lookB[0] = X[0] - Xsc[0];
    lookB[1] = X[1] - Xsc[1];
    lookB[2] = X[2] - Xsc[2];

    std::vector<double> lookJ = bodyFrame->J2000Vector(lookB);
    SpiceRotation *cameraFrame = p_camera->instrumentRotation();
    std::vector<double> lookC = cameraFrame->ReferenceVector(lookJ);

    SpiceDouble unitLookC[3];
    vhat_c(&lookC[0], unitLookC);

    return p_camera->Sensor::SetUniversalGround(lat, lon);
  }

  bool RadarGroundMap::Iterate(SpiceDouble &R, const double &slantRangeSqr, const SpiceDouble c[],
                               const SpiceDouble r[], SpiceDouble X[], SpiceDouble &lat,
                               SpiceDouble &lon, const std::vector<double> &Xsc,
                               const bool &useSlopeEqn, const double &slope) {

    lat = DBL_MAX;
    lon = DBL_MAX;
    SpiceDouble lastR = DBL_MAX;
    SpiceDouble rlat;
    SpiceDouble rlon;
    int iter = 0;
    do {
      double normXsc = vnorm_c(&Xsc[0]);
      double alpha = (R * R - slantRangeSqr - normXsc * normXsc) /
                     (2.0 * vdot_c(&Xsc[0], c));

      double arg = slantRangeSqr - alpha * alpha;
      if(arg < 0.0) return false;

      double beta = sqrt(arg);
      if(p_lookDirection == Radar::Left) beta *= -1.0;

      SpiceDouble alphac[3], betar[3];
      vscl_c(alpha, c, alphac);
      vscl_c(beta, r, betar);

      vadd_c(alphac, betar, alphac);
      vadd_c(&Xsc[0], alphac, X);

      // Convert X to lat,lon
      lastR = R;
      reclat_c(X, &R, &lon, &lat);

      rlat = lat * 180.0 / Isis::PI;
      rlon = lon * 180.0 / Isis::PI;
      if(useSlopeEqn) {
        R = lastR + slope * (p_camera->LocalRadius(rlat, rlon).kilometers() - lastR);
      } else {
        R = p_camera->LocalRadius(rlat, rlon).kilometers();
      }
      
      iter++;
    }
    while(fabs(R - lastR) > p_tolerance && iter < 100);

    if(fabs(R - lastR) > p_tolerance) return false;
 
    return true;
  }

  bool RadarGroundMap::SetGround(const Latitude &lat, const Longitude &lon) {
    Distance localRadius(p_camera->LocalRadius(lat, lon));

    if(!localRadius.isValid()) {
      return false;
    }

    return SetGround(SurfacePoint(lat, lon, p_camera->LocalRadius(lat, lon)));
  }

  bool RadarGroundMap::SetGround(const SurfacePoint &surfacePoint) {
    // Get the ground point in rectangular coordinates (X)
    if(!surfacePoint.Valid()) return false;

    SpiceDouble X[3];
    surfacePoint.ToNaifArray(X);

    // Compute lower bound for Doppler shift
    double et1 = p_camera->Spice::cacheStartTime().Et();
    p_camera->Sensor::setTime(et1);
    double xv1 = ComputeXv(X);

    // Compute upper bound for Doppler shift
    double et2 = p_camera->Spice::cacheEndTime().Et();
    p_camera->Sensor::setTime(et2);
    double xv2 = ComputeXv(X);

    // Make sure we bound root (xv = 0.0)
    if((xv1 < 0.0) && (xv2 < 0.0)) return false;
    if((xv1 > 0.0) && (xv2 > 0.0)) return false;

    // Order the bounds
    double fl, fh, xl, xh;
    if(xv1 < xv2) {
      fl = xv1;
      fh = xv2;
      xl = et1;
      xh = et2;
    }
    else {
      fl = xv2;
      fh = xv1;
      xl = et2;
      xh = et1;
    }

    // Iterate a max of 30 times
    for(int j = 0; j < 30; j++) {
      // Use the secant method to guess the next et
      double etGuess = xl + (xh - xl) * fl / (fl - fh);

      // Compute the guessed Doppler shift.  Hopefully
      // this guess converges to zero at some point
      p_camera->Sensor::setTime(etGuess);
      double fGuess = ComputeXv(X);

      // Update the bounds
      double delTime;
      if(fGuess < 0.0) {
        delTime = xl - etGuess;
        xl = etGuess;
        fl = fGuess;
      }
      else {
        delTime = xh - etGuess;
        xh = etGuess;
        fh = fGuess;
      }

      // See if we are done
      if((fabs(delTime) <= p_timeTolerance) || (fGuess == 0.0)) {
        SpiceRotation *bodyFrame = p_camera->bodyRotation();
        SpicePosition *spaceCraft = p_camera->instrumentPosition();

        // Get body fixed spacecraft velocity and position
        std::vector<double> Ssc(6);

        // Load the state into Ssc and rotate to body-fixed
        vequ_c((SpiceDouble *) & (spaceCraft->Coordinate()[0]), &Ssc[0]);
        vequ_c((SpiceDouble *) & (spaceCraft->Velocity()[0]), &Ssc[3]);
        std::vector<double> bfSsc(6);
        bfSsc = bodyFrame->ReferenceVector(Ssc);

        // Extract the body-fixed position and velocity from the state
        std::vector<double> Vsc(3);
        std::vector<double> Xsc(3);
        vequ_c(&bfSsc[0], (SpiceDouble *) & (Xsc[0]));
        vequ_c(&bfSsc[3], (SpiceDouble *) & (Vsc[0]));

        // Determine if focal plane coordinate falls on the correct side of the
        // spacecraft. Radar has both left and right look directions. Make sure
        // the coordinate is on the same side as the look direction. This is done
        // by (X - S) . (V x S) where X=ground point vector, S=spacecraft position
        // vector, and V=velocity vector. If the dot product is greater than 0, then
        // the point is on the right side. If the dot product is less than 0, then
        // the point is on the left side. If the dot product is 0, then the point is
        // directly under the spacecraft (neither left or right) and is invalid.
        SpiceDouble vout1[3];
        SpiceDouble vout2[3];
        SpiceDouble dp;
        vsub_c(X, &Xsc[0], vout1);
        vcrss_c(&Vsc[0], &Xsc[0], vout2);
        dp = vdot_c(vout1, vout2);
        if(dp > 0.0 && p_lookDirection == Radar::Left) return false;
        if(dp < 0.0 && p_lookDirection == Radar::Right) return false;
        if(dp == 0.0) return false;



        // Compute body fixed look direction
        std::vector<double> lookB;
        lookB.resize(3);
        lookB[0] = X[0] - Xsc[0];
        lookB[1] = X[1] - Xsc[1];
        lookB[2] = X[2] - Xsc[2];

        std::vector<double> lookJ = bodyFrame->J2000Vector(lookB);
        SpiceRotation *cameraFrame = p_camera->instrumentRotation(); //this is the pointer to the camera's SpiceRotation/instrumentatrotation object
        std::vector<double> lookC = cameraFrame->ReferenceVector(lookJ);

        SpiceDouble unitLookC[3];
        vhat_c(&lookC[0], unitLookC);

        p_camera->SetFocalLength(p_slantRange * 1000.0); // p_slantRange is km so focal length is in m
        p_focalPlaneX = p_slantRange * 1000.0 / p_rangeSigma; // km to meters and scaled to focal plane
        p_focalPlaneY = 0.0;
        p_camera->target()->shape()->setSurfacePoint(surfacePoint); // Added 2-11-2013 by DAC

        // set the sensor's ground point and also makes it possible to calculate m_ra & m_dec

        return p_camera->Sensor::SetGround(surfacePoint, true);
      }
    }

    return false;
  }


  bool RadarGroundMap::GetXY(const SurfacePoint &spoint, double *cudx,
                             double *cudy) {

    // Get the ground point in rectangular body-fixed coordinates (X)
    double X[3];
    X[0] = spoint.GetX().kilometers();
    X[1] = spoint.GetY().kilometers();
    X[2] = spoint.GetZ().kilometers();

    // Compute body-fixed look vector
    SpiceRotation *bodyFrame = p_camera->bodyRotation();
    SpicePosition *spaceCraft = p_camera->instrumentPosition();

    std::vector<double> sJ(6);   // Spacecraft state vector (position and velocity) in J2000 frame
    // Load the state into sJ
    vequ_c((SpiceDouble *) & (spaceCraft->Coordinate()[0]), &sJ[0]);
    vequ_c((SpiceDouble *) & (spaceCraft->Velocity()[0]), &sJ[3]);

    // Rotate the state to body-fixed
    p_sB.resize(6);
    p_sB = bodyFrame->ReferenceVector(sJ);

    // Extract the body-fixed position and velocity
    SpiceDouble VsB[3];
    SpiceDouble PsB[3];
    vequ_c(&p_sB[0], PsB);
    vequ_c(&p_sB[3], VsB);

    p_lookB.resize(3);
    vsub_c(X, PsB, &p_lookB[0]);

    p_groundSlantRange = vnorm_c(&p_lookB[0]);  // km
    p_groundDopplerFreq = 2. / p_waveLength / p_groundSlantRange * vdot_c(&p_lookB[0], &VsB[0]);
    *cudx = p_groundSlantRange * 1000.0 / p_rangeSigma;  // to meters, then to focal plane coord
    *cudy = p_groundDopplerFreq / p_dopplerSigma;   // htx to focal plane coord

    return true;
  }


  double RadarGroundMap::ComputeXv(SpiceDouble X[3]) {
    // Get the spacecraft position (Xsc) and velocity (Vsc) in body fixed
    // coordinates
    SpiceRotation *bodyFrame = p_camera->bodyRotation();
    SpicePosition *spaceCraft = p_camera->instrumentPosition();

    // Load the state into Ssc
    std::vector<double> Ssc(6);
    vequ_c((SpiceDouble *) & (spaceCraft->Coordinate()[0]), &Ssc[0]);
    vequ_c((SpiceDouble *) & (spaceCraft->Velocity()[0]), &Ssc[3]);

    // Rotate the state to body-fixed
    std::vector<double> bfSsc(6);
    bfSsc = bodyFrame->ReferenceVector(Ssc);

    // Extract the body-fixed position and velocity
    std::vector<double> Vsc(3);
    std::vector<double> Xsc(3);
    vequ_c(&bfSsc[0], &Xsc[0]);
    vequ_c(&bfSsc[3], &Vsc[0]);

    // Compute the slant range
    SpiceDouble lookB[3];
    vsub_c(&Xsc[0], X, lookB);
    p_slantRange = vnorm_c(lookB);   // units are km

    // Compute and return xv = -2 * (point - observer) dot (point velocity - observer velocity) / (slantRange*wavelength)
    // In body-fixed coordinates, the point velocity = 0. so the equation becomes
    //    double xv = 2.0 * vdot_c(lookB,&Vsc[0]) / (vnorm_c(lookB) * WaveLength() );
    double xv = -2.0 * vdot_c(lookB, &Vsc[0]) / (vnorm_c(lookB) * WaveLength()); // - is applied to lookB above
    return xv;
  }


  // d_slantRange = (lookB dot d_lookB) / slantRange
  // d_dopplerFrequency = -dopplerFrequency/slantRange*d_slantRange -
  //                      2./wavelength/slantRange*(d_lookB dot vlookB) -
  //                      2./wavelength/slantRange*(lookB dot d_vlookB)

  // Add the partial for the x coordinate of the position (differentiating
  // point(x,y,z) - spacecraftPosition(x,y,z) in body-fixed and the velocity
  // Load the derivative of the state into d_lookJ
  bool RadarGroundMap::GetdXYdPosition(const SpicePosition::PartialType varType, int coefIndex,
                                       double *dx, double *dy) {
    SpicePosition *instPos = p_camera->instrumentPosition();
    SpiceRotation *bodyRot = p_camera->bodyRotation();

    std::vector <double> d_lookJ(6);
    vequ_c(&(instPos->CoordinatePartial(varType, coefIndex))[0], &d_lookJ[0]);
    vequ_c(&(instPos->VelocityPartial(varType, coefIndex))[0], &d_lookJ[3]);

    std::vector<double> d_lookB =  bodyRot->ReferenceVector(d_lookJ);

    double d_slantRange = (-1.) * vdot_c(&p_lookB[0], &d_lookB[0]) / p_groundSlantRange;
    double d_dopplerFreq = (-1.) * p_groundDopplerFreq * d_slantRange / p_groundSlantRange -
                           2. / p_waveLength / p_groundSlantRange * vdot_c(&d_lookB[0], &p_sB[3]) +
                           2. / p_waveLength / p_groundSlantRange * vdot_c(&p_lookB[0], &d_lookB[3]);

    *dx = d_slantRange * 1000.0 / p_rangeSigma;// km to meters, then to focal plane coord
    *dy = d_dopplerFreq / p_dopplerSigma;   // htz scaled to focal plane

    return true;
  }

  bool RadarGroundMap::GetdXYdPoint(std::vector<double> d_lookB,
                                    double *dx, double *dy) {

    //  TODO  add a check to make sure p_lookB has been set

    double d_slantRange = vdot_c(&p_lookB[0], &d_lookB[0]) / p_groundSlantRange;  // km
    // After switching to J2000, the last term will not be 0. as it is in body-fixed
//    double d_dopplerFreq = p_groundDopplerFreq*d_slantRange/p_groundSlantRange // Ken
//      + 2./p_waveLength/p_groundSlantRange*vdot_c(&d_lookB[0], &p_sB[3]);
    double d_dopplerFreq = (-1.) * p_groundDopplerFreq * d_slantRange / p_groundSlantRange
                           + 2. / p_waveLength / p_groundSlantRange * vdot_c(&d_lookB[0], &p_sB[3]);
//        + 2./p_wavelength/slantRange*vdot_c(&p_lookB[0], 0);

    *dx = d_slantRange * 1000.0 / p_rangeSigma;
    *dy = d_dopplerFreq / p_dopplerSigma;

    return true;
  }

}