lsst::meas::extensions::trailedSources::VeresModel Class Reference

Implementation of an axisymmetric 2D Gaussian convolved with a line – a model for a fast-moving, trailed-source (Veres et al. More...

#include <VeresModel.h>

Public Types
using	ImageF = afw::image::Image< float >
using	ExposureF = afw::image::Exposure< float >

Public Member Functions
	VeresModel (ExposureF const &data)
	Constructor for VeresModel. More...
	VeresModel (VeresModel const &)=default
	VeresModel (VeresModel &&)=default
VeresModel &	operator= (VeresModel const &)=default
VeresModel &	operator= (VeresModel &&)=default
	~VeresModel ()=default
double	operator() (std::vector< double > const &params) const
	Compute chi-squared of the model given the data. More...
std::vector< double >	gradient (std::vector< double > const &params) const
	Compute the gradient of chi-squared of the model given the data. More...
double	getSigma () const noexcept
	Return the PSF sigma. More...

Detailed Description

Implementation of an axisymmetric 2D Gaussian convolved with a line – a model for a fast-moving, trailed-source (Veres et al.

2012).

VeresModel is designed to compute the chi-squared of the model given an lsst::afw::image::Exposure.

Definition at line 47 of file VeresModel.h.

Member Typedef Documentation

ExposureF

using lsst::meas::extensions::trailedSources::VeresModel::ExposureF = afw::image::Exposure<float>

Definition at line 50 of file VeresModel.h.

ImageF

using lsst::meas::extensions::trailedSources::VeresModel::ImageF = afw::image::Image<float>

Definition at line 49 of file VeresModel.h.

Constructor & Destructor Documentation

VeresModel() [1/3]

lsst::meas::extensions::trailedSources::VeresModel::VeresModel ( ExposureF const &  data )

explicit

Constructor for VeresModel.

Parameters

data	Exposure passed from the measurement task.

Definition at line 39 of file VeresModel.cc.

  : _sigma(data.getPsf()->computeShape().getTraceRadius()),
    _bbox(data.getBBox()),
    _data(data.getMaskedImage().getImage()->getArray()),
    _variance(data.getMaskedImage().getVariance()->getArray()) {}

VeresModel() [2/3]

lsst::meas::extensions::trailedSources::VeresModel::VeresModel ( VeresModel const &  )

default

VeresModel() [3/3]

lsst::meas::extensions::trailedSources::VeresModel::VeresModel ( VeresModel &&  )

default

~VeresModel()

lsst::meas::extensions::trailedSources::VeresModel::~VeresModel ( )

default

Member Function Documentation

getSigma()

double lsst::meas::extensions::trailedSources::VeresModel::getSigma ( ) const

inlinenoexcept

Return the PSF sigma.

Definition at line 99 of file VeresModel.h.

{ return _sigma; }

gradient()

std::vector< double > lsst::meas::extensions::trailedSources::VeresModel::gradient

(

std::vector< double > const &

params

)

const

Compute the gradient of chi-squared of the model given the data.

Parameters

params

Model parameters.

Returns

The gradient of chi-squared of the model with respect to the model parameters.

Note

The params vector contains the following model parameters:

• Centroid x: X-coordinate of the centroid in given image [pixels].
• Centroid y: Y-coordinate of the centroid in given image [pixels].
• Flux: Total flux in the trail [count].
• Length: Length of the trail [pixels].
• Angle: Angle from the +x-axis [radians].

Definition at line 70 of file VeresModel.cc.

                                                                            {
 
    double xc = params[0];     // Centroid x
    double yc = params[1];     // Centroid y
    double flux = params[2];   // Flux
    double length = params[3]; // Trail length
    double theta = params[4];  // Angle from +x-axis
 
    // Compute gradients of the model and of chi-squared
    std::vector<double> gradChiSq = {0.0,0.0,0.0,0.0,0.0};
    for (int yIndex = 0, yp = _bbox.getBeginY(); yIndex < _bbox.getHeight(); ++yIndex, ++yp) {
        ImageF::Array::Reference dataRow = _data[yIndex];
        ImageF::Array::Reference varRow = _variance[yIndex];
        for (int xIndex = 0, xp = _bbox.getBeginX(); xIndex < _bbox.getWidth(); ++xIndex, ++xp) {
            double model = _computeModel(xp,yp,xc,yc,flux,length,theta);
            double gradDiff = -2.0 * (dataRow[xIndex] - model) / varRow[xIndex];
            std::array<double, 5> gradModel = _computeGradient(xp,yp,xc,yc,flux,length,theta);
            for (int k=0; k<5; ++k) {
                gradChiSq[k] += gradModel[k] * gradDiff;
            }
        }
    }
    return gradChiSq;
}

operator()()

double lsst::meas::extensions::trailedSources::VeresModel::operator()

(

std::vector< double > const &

params

)

const

Compute chi-squared of the model given the data.

Parameters

params

Model parameters.

Returns

The chi-squared of the model.

Note

The params vector contains the following model parameters:

• Centroid x: X-coordinate of the centroid in given image [pixels].
• Centroid y: Y-coordinate of the centroid in given image [pixels].
• Flux: Total flux in the trail [count].
• Length: Length of the trail [pixels].
• Angle: Angle from the +x-axis [radians].

Definition at line 46 of file VeresModel.cc.

                                                                   {
 
    double xc = params[0];     // Centroid x
    double yc = params[1];     // Centroid y
    double flux = params[2];   // Flux
    double length = params[3]; // Trail length
    double theta = params[4];  // Angle from +x-axis
 
    // Compute model image and chi-squared
    double chiSq = 0.0;
    // Loop is adapted from lsst::afw::detection::Psf::computeKernelImage()
    for (int yIndex = 0, yp = _bbox.getBeginY(); yIndex < _bbox.getHeight(); ++yIndex, ++yp) {
        ImageF::Array::Reference dataRow = _data[yIndex];
        ImageF::Array::Reference varRow = _variance[yIndex];
        for (int xIndex = 0, xp = _bbox.getBeginX(); xIndex < _bbox.getWidth(); ++xIndex, ++xp) {
            double model = _computeModel(xp,yp,xc,yc,flux,length,theta);
            double diff = dataRow[xIndex] - model;
            chiSq += diff*diff/varRow[xIndex];
        }
    }
 
    return chiSq;
}

operator=() [1/2]

VeresModel& lsst::meas::extensions::trailedSources::VeresModel::operator= ( VeresModel &&  )

default

operator=() [2/2]

VeresModel& lsst::meas::extensions::trailedSources::VeresModel::operator= ( VeresModel const &  )

default

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The documentation for this class was generated from the following files:

• /j/snowflake/release/lsstsw/stack/lsst-scipipe-0.7.0/Linux64/meas_extensions_trailedSources/master-g72cdda8301+729191ecac/include/lsst/meas/extensions/trailedSources/VeresModel.h
• /j/snowflake/release/lsstsw/stack/lsst-scipipe-0.7.0/Linux64/meas_extensions_trailedSources/master-g72cdda8301+729191ecac/src/VeresModel.cc