wcs

Documentation

Index

• func ComputeAffineTransformation(matches []spatial.QuadMatch) (transform.Affine2DParameters, float64, float64, error)
• type CTypeP
• type CoordinateProjectionType
  • func (c CoordinateProjectionType) ToCTypes() CTypeP
• type PointPair
• type WCS
  • func NewWorldCoordinateSystem(xc float64, yc float64, params WCSParams) WCS
  • func (wcs *WCS) EquatorialCoordinateToPixel(ra, dec float64) (x, y float64)
  • func (wcs *WCS) PixelToEquatorialCoordinate(x, y float64) (coordinate astrometry.ICRSEquatorialCoordinate)
  • func (wcs *WCS) SolveForCentroid() (coordinate astrometry.ICRSEquatorialCoordinate)
• type WCSParams

Functions

func ComputeAffineTransformation

func ComputeAffineTransformation(matches []spatial.QuadMatch) (transform.Affine2DParameters, float64, float64, error)

ComputeAffineTransformation computes the affine transformation parameters based on matched quads. It returns the affine parameters and an error if the computation fails.

Types

type CTypeP

type CTypeP struct {
	CType1 string
	CType2 string
}

type CoordinateProjectionType

type CoordinateProjectionType int

const (
	RADEC_TAN CoordinateProjectionType = iota
	RADEC_TANSIP
)

func (CoordinateProjectionType) ToCTypes

func (c CoordinateProjectionType) ToCTypes() CTypeP

type PointPair

type PointPair struct {
	X, Y    float64 // Generated Quad NormalisedC and NormalisedD
	RA, Dec float64 // Source Quad SourceRA and SourceDec
}

Each match provides two point correspondences: C and D

type WCS

type WCS struct {
	WCAXES int                              `hdu:"WCAXES" default:"2"`        // Number of world coordinate axes
	CRPIX1 float64                          `hdu:"CRPIX1"`                    // Reference pixel X
	CRPIX2 float64                          `hdu:"CRPIX2"`                    // Reference pixel Y
	CRVAL1 float64                          `hdu:"CRVAL1" default:"0.0"`      // Reference RA (example default, often specific to image)
	CRVAL2 float64                          `hdu:"CRVAL2" default:"0.0"`      // Reference Dec (example default, often specific to image)
	CTYPE1 string                           `hdu:"CTYPE1" default:"RA---TAN"` // Coordinate type for axis 1, typically RA with TAN projection
	CTYPE2 string                           `hdu:"CTYPE2" default:"DEC--TAN"` // Coordinate type for axis 2, typically DEC with TAN projection
	CDELT1 float64                          `hdu:"CDELT1"`                    // Coordinate increment for axis 1 (no default)
	CDELT2 float64                          `hdu:"CDELT2"`                    // Coordinate increment for axis 2 (no default)
	CUNIT1 string                           `hdu:"CUNIT1" default:"deg"`      // Coordinate unit for axis 1, defaulted to degrees
	CUNIT2 string                           `hdu:"CUNIT2" default:"deg"`      // Coordinate unit for axis 2, defaulted to degrees
	CD1_1  float64                          `hdu:"CD1_1"`                     // Affine transform parameter A (no default)
	CD1_2  float64                          `hdu:"CD1_2"`                     // Affine transform parameter B (no default)
	CD2_1  float64                          `hdu:"CD2_1"`                     // Affine transform parameter C (no default)
	CD2_2  float64                          `hdu:"CD2_2"`                     // Affine transform parameter D (no default)
	E      float64                          `hdu:"E"`                         // Affine translation parameter e (optional, no default)
	F      float64                          `hdu:"F"`                         // Affine translation parameter f (optional, no default)
	FSIP   transform.SIP2DForwardParameters ``                                // SIP forward transformation (distortion) coefficients
	ISIP   transform.SIP2DInverseParameters ``                                // SIP inverse transformation (distortion) coefficients
}

func NewWorldCoordinateSystem

func NewWorldCoordinateSystem(xc float64, yc float64, params WCSParams) WCS

NewWorldCoordinateSystem creates a new WCS object with correctly mapped affine parameters.

func (*WCS) EquatorialCoordinateToPixel

func (wcs *WCS) EquatorialCoordinateToPixel(
	ra, dec float64,
) (x, y float64)

without iterative removal of SIP distortions.

func (*WCS) PixelToEquatorialCoordinate

func (wcs *WCS) PixelToEquatorialCoordinate(
	x, y float64,
) (coordinate astrometry.ICRSEquatorialCoordinate)

func (*WCS) SolveForCentroid

func (wcs *WCS) SolveForCentroid() (coordinate astrometry.ICRSEquatorialCoordinate)

type WCSParams

type WCSParams struct {
	Projection       CoordinateProjectionType         // Projection type e.g., "TAN", or "TAN-SIP"
	AffineParams     transform.Affine2DParameters     // Affine transformation parameters
	ReferenceX       float64                          // Reference X coordinate
	ReferenceY       float64                          // Reference Y coordinate
	SIPForwardParams transform.SIP2DForwardParameters // SIP forward transformation (distortion) coefficients, x, y to RA, Dec
	SIPInverseParams transform.SIP2DInverseParameters // SIP inverse transformation (distortion) coefficients RA, Dec to x, y
}