lsst.afw.geom.skyWcs.SkyWcs Class Reference

Public Member Functions
def	pixelToSkyArray (self, x, y, degrees=False)
def	skyToPixelArray (self, ra, dec, degrees=False)
def	getRelativeRotationToWcs (self, otherWcs)

Detailed Description

Definition at line 40 of file skyWcs.py.

Member Function Documentation

getRelativeRotationToWcs()

def lsst.afw.geom.skyWcs.SkyWcs.getRelativeRotationToWcs	(		self,
			otherWcs
	)

Get the difference in sky rotation angle to the specified wcs.

Ignoring location on the sky, if another wcs were atop this one,
what would the difference in rotation be? i.e. for

otherWcs = createInitialSkyWcsFromBoresight(radec, rotation, detector)

what is the value that needs to be added to ``self.rotation`` (or
subtracted from `other.rotation``) to align them?

Parameters
----------
otherWcs : `lsst.afw.geom.SkyWcs`
    The wcs to calculate the angle to.

Returns
-------
angle : `lsst.geom.Angle`
    The angle between this and the supplied wcs,
    over the half-open range [0, 2pi).

Definition at line 104 of file skyWcs.py.

    def getRelativeRotationToWcs(self, otherWcs):
        """Get the difference in sky rotation angle to the specified wcs.
 
        Ignoring location on the sky, if another wcs were atop this one,
        what would the difference in rotation be? i.e. for
 
        otherWcs = createInitialSkyWcsFromBoresight(radec, rotation, detector)
 
        what is the value that needs to be added to ``self.rotation`` (or
        subtracted from `other.rotation``) to align them?
 
        Parameters
        ----------
        otherWcs : `lsst.afw.geom.SkyWcs`
            The wcs to calculate the angle to.
 
        Returns
        -------
        angle : `lsst.geom.Angle`
            The angle between this and the supplied wcs,
            over the half-open range [0, 2pi).
        """
        # Note: tests for this function live in
        # obs_lsst/tests/test_afwWcsUtil.py due to the need for an easy
        # constructor and instantiated detector, and the fact that afw
        # cannot depend on obs_base or obs_lsst.
 
        m1 = self.getCdMatrix()
        m2 = otherWcs.getCdMatrix()
 
        svd1 = scipy.linalg.svd(m1)
        svd2 = scipy.linalg.svd(m2)
 
        m1rot = np.matmul(svd1[0], svd1[2])
        m2rot = np.matmul(svd2[0], svd2[2])
 
        v_rot = [1, 0]
 
        v_rot = np.matmul(v_rot, m1rot)  # rotate by wcs1
        v_rot = np.matmul(v_rot, m2rot.T)  # rotate _back_ by wcs2
 
        rotation = np.arctan2(v_rot[1], v_rot[0])
        rotation = rotation % (2*np.pi)
        return lsst.geom.Angle(rotation, lsst.geom.radians)
 
 
SkyWcs.__reduce__ = reduceTransform

pixelToSkyArray()

def lsst.afw.geom.skyWcs.SkyWcs.pixelToSkyArray	(		self,
			x,
			y,
			degrees = False
	)

Convert numpy array pixels (x, y) to numpy array sky (ra, dec)
positions.

Parameters
----------
x : `np.ndarray`
    Array of x values.
y : `np.ndarray`
    Array of y values.
degrees : `bool`, optional
    Return ra, dec arrays in degrees if True.

Returns
-------
ra : `np.ndarray`
    Array of Right Ascension.  Units are radians unless
    degrees=True.
dec : `np.ndarray`
    Array of Declination.  Units are radians unless
    degrees=True.

Definition at line 41 of file skyWcs.py.

    def pixelToSkyArray(self, x, y, degrees=False):
        """
        Convert numpy array pixels (x, y) to numpy array sky (ra, dec)
        positions.
 
        Parameters
        ----------
        x : `np.ndarray`
            Array of x values.
        y : `np.ndarray`
            Array of y values.
        degrees : `bool`, optional
            Return ra, dec arrays in degrees if True.
 
        Returns
        -------
        ra : `np.ndarray`
            Array of Right Ascension.  Units are radians unless
            degrees=True.
        dec : `np.ndarray`
            Array of Declination.  Units are radians unless
            degrees=True.
        """
        xy = np.vstack((x, y))
        ra, dec = np.vsplit(self.getTransform().getMapping().applyForward(xy), 2)
        ra %= (2.*np.pi)
 
        if degrees:
            return np.rad2deg(ra.ravel()), np.rad2deg(dec.ravel())
        else:
            return ra.ravel(), dec.ravel()
 

skyToPixelArray()

def lsst.afw.geom.skyWcs.SkyWcs.skyToPixelArray	(		self,
			ra,
			dec,
			degrees = False
	)

Convert numpy array sky (ra, dec) positions to numpy array
pixels (x, y).

Parameters
----------
ra : `np.ndarray`
    Array of Right Ascension.  Units are radians unless
    degrees=True.
dec : `np.ndarray`
    Array of Declination.  Units are radians unless
    degrees=True.
degrees : `bool`, optional
    Input ra, dec arrays are degrees if True.

Returns
-------
x : `np.ndarray`
    Array of x values.
y : `np.ndarray`
    Array of y values.

Definition at line 73 of file skyWcs.py.

    def skyToPixelArray(self, ra, dec, degrees=False):
        """
        Convert numpy array sky (ra, dec) positions to numpy array
        pixels (x, y).
 
        Parameters
        ----------
        ra : `np.ndarray`
            Array of Right Ascension.  Units are radians unless
            degrees=True.
        dec : `np.ndarray`
            Array of Declination.  Units are radians unless
            degrees=True.
        degrees : `bool`, optional
            Input ra, dec arrays are degrees if True.
 
        Returns
        -------
        x : `np.ndarray`
            Array of x values.
        y : `np.ndarray`
            Array of y values.
        """
        radec = np.vstack((ra, dec))
        if degrees:
            radec = np.deg2rad(radec)
 
        x, y = np.vsplit(self.getTransform().getMapping().applyInverse(radec), 2)
 
        return x.ravel(), y.ravel()
 

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

• /j/snowflake/release/lsstsw/stack/lsst-scipipe-0.7.0/Linux64/afw/22.0.1-42-gca6935d93+ba5e5ca3eb/python/lsst/afw/geom/skyWcs.py