bool IrAtmosphere1::calculateAtmosphereContribution(IrQueryMsg* const msg, LCreal* totalSignal, LCreal* totalBackground)
{
// Sum the total signal that reaches the seeker of the target represented by the message
// and the background noise observed by the seeker
const LCreal* centerWavelengths = getWaveBandCenters();
const LCreal* widths = getWaveBandWidths();
const LCreal* sigArray = msg->getSignatureByWaveband();
const Player* ownship = msg->getOwnship();
const Player* target = msg->getTarget();
// FAB - this should be angle of gimbal, not angle to target. (see base class)
// Determine the angle above the horizon to be used for background radiation lookup
const LCreal range2D = msg->getRange();
const LCreal tanPhi = static_cast<LCreal>( (target->getAltitudeM() - ownship->getAltitudeM())/ range2D );
const LCreal tanPhiPrime = tanPhi - ( range2D / 12756776.0f ); // Twice earth radius
// appears that negative angles are down in this calculation
LCreal viewingAngle = lcAtan(tanPhiPrime);
// table limits are 0 to pi; this correction assumes that 0 in the table is straight down, PI is straight up
viewingAngle += PI/2.0;
*totalSignal = 0.0;
*totalBackground = 0.0;
for (unsigned int i=0; i<getNumWaveBands(); i++) {
const LCreal lowerBandBound = centerWavelengths[i] - (widths[i] / 2.0f);
const LCreal upperBandBound = lowerBandBound + widths[i];
// determine ratio of this band's coverage to entire atmosphere waveband
const LCreal fractionOfBandToTotal = (upperBandBound - lowerBandBound) / ((centerWavelengths[getNumWaveBands() - 1] + (widths[getNumWaveBands() - 1] / 2.0f))-(centerWavelengths[0] - (widths[0] / 2.0f)));
// Find the limits of the sensor
const LCreal lowerSensorBound = msg->getLowerWavelength();
const LCreal upperSensorBound = msg->getUpperWavelength();
// Determine how much of this wave band overlaps the sensor limits
const LCreal lowerOverlap = getLowerEndOfWavelengthOverlap(lowerBandBound, lowerSensorBound);
LCreal upperOverlap = getUpperEndOfWavelengthOverlap(upperBandBound, upperSensorBound);
if (upperOverlap < lowerOverlap) upperOverlap = lowerOverlap;
const LCreal overlapRatio = (upperOverlap - lowerOverlap) / (upperBandBound - lowerBandBound);
// Get the background radiation given the sensor altitude and the viewing angle
LCreal backgroundRadianceInBand = overlapRatio * getBackgroundRadiation(
lowerBandBound,
upperBandBound,
static_cast<LCreal>(ownship->getAltitudeM()),
viewingAngle);
LCreal radiantIntensityInBin(0.0);
if (sigArray == 0) {
// signature is a simple number
// distribute simple signature evenly across atmosphere bins
// need to apply overlapRatio to simple signature - already applied for complex signature in IrSignature...
radiantIntensityInBin = msg->getSignatureAtRange() * fractionOfBandToTotal * overlapRatio;
}
else {
// Find the limits of the bin
//lowerBandBound = sigArray [i*3];
//upperBandBound = sigArray [i*3 + 1] ;
// assuming that signature bands match atmosphere bands
radiantIntensityInBin = sigArray[i*3 + 2];
}
// add in reflected solar radiation
const LCreal solarRadiationInBin = ((1.0f - msg->getEmissivity()) * getSolarRadiation(centerWavelengths[i],
static_cast<LCreal>(target->getAltitudeM())));
radiantIntensityInBin += (solarRadiationInBin * overlapRatio);
// Lookup the transmissivity in the wave band given the altitudes of sensor
// and target and the ground range between the two
const LCreal transmissivity = getTransmissivity(
lowerBandBound,
upperBandBound,
static_cast<LCreal>(ownship->getAltitudeM()),
static_cast<LCreal>(target->getAltitudeM()),
range2D);
*totalSignal += radiantIntensityInBin * transmissivity;
// Add the background radiance from the this waveband within the sensor limits
// to the total background radiance received by the sensor, watts/sr-m^2
*totalBackground += backgroundRadianceInBand * transmissivity;
}
return true;
}
bool IrAtmosphere::calculateAtmosphereContribution(IrQueryMsg* const msg, LCreal* totalSignal, LCreal* totalBackground)
{
const LCreal* centerWavelengths = getWaveBandCenters();
const LCreal* widths = getWaveBandWidths();
LCreal totalWavelengthRange = ((centerWavelengths[getNumWaveBands() - 1] + (widths[getNumWaveBands() - 1] / 2.0f))-(centerWavelengths[0] - (widths[0] / 2.0f)));
const LCreal* sigArray = msg->getSignatureByWaveband();
LCreal range2D = msg->getRange();
*totalSignal = 0.0;
*totalBackground = 0.0;
LCreal backgroundRadiance = 0.0;
// determine relation of FOV to horizon, to decide how much earth and how much sky in background
{
LCreal currentViewAngle;
LCreal viewAngleToHorizon;
// viewAngleToTarget is angle to target, not angle my sensor is actually pointing.
// we want the fov i'm actually pointing at, not a FOV centred on each target
// determine elevation angle to target, negative angles are down
//{
// //Player* ownship = msg->getOwnship();
// // Determine the angle above the horizon to be used for background radiation lookup
// LCreal range2D = msg->getRange();
// LCreal tanPhi = (LCreal)( (msg->getTarget()->getAltitudeM() - msg->getOwnship()->getAltitudeM())/ range2D );
// LCreal tanPhiPrime = tanPhi - ( range2D / 12756776.0f ); // Twice earth radius
// // appears that negative angles are down in this calculation
// currentViewAngle = lcAtan(tanPhiPrime);
// // table limits are 0 to pi; this correction assumes that 0 in the table is straight down, PI is straight up
// //viewAngleToTarget += PI/2.0;
//}
// determine elevation angle of gimbal/ownship, negative angles are down
{
osg::Vec3d angles;
osg::Matrixd mm = msg->getGimbal()->getRotMat() * msg->getOwnship()->getRotMat();
// compute Geodetic orientation angles
Basic::Nav::computeEulerAngles(mm, &angles);
currentViewAngle = angles[Player::IPITCH];
}
// FAB determine angle to horizon, positive angles are down
{
double hDist = 1000000.0 * Basic::Distance::NM2M; // Distance to horizon (m) (default: really far away)
double hTanAng = 0;
// earth radius in meters
double er = Basic::Nav::ERAD60 * Basic::Distance::NM2M;
// distance from the center of the earth
double distEC = msg->getOwnship()->getAltitudeM() + er;
double distEC2 = distEC * distEC; // squared
// earth radius squared
double er2 = er * er;
// distance to horizon squared
double dh2 = distEC2 - er2;
// the distance and the tangent of the angle to the horizon
hDist = sqrt(dh2);
hTanAng = ( hDist / er ); // positive angles are below level (down)
viewAngleToHorizon = lcAtan(hTanAng);
}
// determine ratio of earth and sky in the FOV
LCreal angleToHorizon = currentViewAngle + viewAngleToHorizon;
LCreal fovtheta = msg->getSendingSensor()->getIFOVTheta();
if (angleToHorizon - fovtheta >= 0) {
// no ground, all sky?
backgroundRadiance = getSkyRadiance();
}
else if (fovtheta - angleToHorizon >= 2*fovtheta) {
// all ground, no sky?
backgroundRadiance = getEarthRadiance();
}
else {
// looking at ground & sky
LCreal ratio = 0.5 + 0.5*angleToHorizon/fovtheta; // convert range of -1 to 1 noninclusive to range of 0 to 1 noninclusive
backgroundRadiance = ratio*getSkyRadiance() + (1.0-ratio)*getEarthRadiance();
}
}
for (unsigned int i=0; i<getNumWaveBands(); i++) {
LCreal radiantIntensityInBin;
LCreal lowerBandBound = centerWavelengths[i] - (widths[i] / 2.0f);
LCreal upperBandBound = lowerBandBound + widths[i];
// determine ratio of this band's coverage to entire atmosphere waveband
LCreal fractionOfBandToTotal = (upperBandBound - lowerBandBound) / totalWavelengthRange;
// Find the limits of the sensor
LCreal lowerSensorBound = msg->getLowerWavelength();
LCreal upperSensorBound = msg->getUpperWavelength();
// Determine how much of this wave band overlaps the sensor limits
LCreal lowerOverlap = getLowerEndOfWavelengthOverlap(
lowerBandBound,
lowerSensorBound);
LCreal upperOverlap = getUpperEndOfWavelengthOverlap(
upperBandBound,
upperSensorBound);
if (upperOverlap < lowerOverlap) upperOverlap = lowerOverlap;
LCreal overlapRatio = (upperOverlap - lowerOverlap) / (upperBandBound - lowerBandBound);
// this depends on whether target is a sky or earth based target
LCreal backgroundRadianceInBand = backgroundRadiance * fractionOfBandToTotal * overlapRatio;
if (sigArray == 0) {
// signature is a simple number
// distribute simple signature evenly across atmosphere bins
// need to apply overlapRatio to simple signature - already applied for complex signature in IrSignature...
radiantIntensityInBin = msg->getSignatureAtRange() * fractionOfBandToTotal * overlapRatio;
}
else {
// if the IrQueryMsg has a sigArray, then the signature is a multi-band signature
// Find the limits of the bin
//lowerBandBound = sigArray [i*3];
//upperBandBound = sigArray [i*3 + 1] ;
// assuming that signature bands match atmosphere bands
radiantIntensityInBin = sigArray[i*3 + 2];
}
LCreal test = getTransmissivity(i, range2D);
*totalSignal += radiantIntensityInBin * getTransmissivity(i, range2D); //* getTransmissivity();
// Add the background radiance from the this waveband within the sensor limits
// to the total background radiance received by the sensor, watts/sr-m^2
*totalBackground += backgroundRadianceInBand * getTransmissivity(i, range2D); //* getTransmissivity();
}
return true;
}
