lsst.skymap.ringsSkyMap.RingsSkyMap Class Reference

Inheritance diagram for lsst.skymap.ringsSkyMap.RingsSkyMap:

Public Member Functions
def	__init__ (self, config, version=1)
def	getRingIndices (self, index)
def	generateTract (self, index)
def	findTract (self, coord)
def	findAllTracts (self, coord)
def	findTractPatchList (self, coordList)
def	updateSha1 (self, sha1)
def	__reduce__ (self)
def	__iter__ (self)
def	__len__ (self)
def	__getitem__ (self, index)
def	findClosestTractPatchList (self, coordList)
def	__hash__ (self)
def	__eq__ (self, other)
def	__ne__ (self, other)
def	logSkyMapInfo (self, log)
def	getSha1 (self)
def	register (self, name, registry)

Public Attributes
	config

Static Public Attributes
	ConfigClass

Detailed Description

Rings sky map pixelization.

We divide the sphere into N rings of Declination, plus the two polar
caps, which sets the size of the individual tracts.  The rings are
divided in RA into an integral number of tracts of this size; this
division is made at the Declination closest to zero so as to ensure
full overlap.

Rings are numbered in the rings from south to north. The south pole cap is
``tract=0``, then the tract at ``raStart`` in the southernmost ring is
``tract=1``. Numbering continues (in the positive RA direction) around that
ring and then continues in the same fashion with the next ring north, and
so on until all reaching the north pole cap, which is
``tract=len(skymap) - 1``.

However, ``version=0`` had a bug in the numbering of the tracts: the first
and last tracts in the first (southernmost) ring were identical, and the
first tract in the last (northernmost) ring was missing. When using
``version=0``, these tracts remain missing in order to preserve the
numbering scheme.

Parameters
----------
config : `lsst.skymap.RingsSkyMapConfig`
    The configuration for this SkyMap.
version : `int`, optional
    Software version of this class, to retain compatibility with old
    verisons. ``version=0`` covers the period from first implementation
    until DM-14809, at which point bugs were identified in the numbering
    of tracts (affecting only tracts at RA=0). ``version=1`` uses the
    post-DM-14809 tract numbering.

Definition at line 41 of file ringsSkyMap.py.

Constructor & Destructor Documentation

__init__()

def lsst.skymap.ringsSkyMap.RingsSkyMap.__init__	(		self,
			config,
			version = 1
	)

Definition at line 77 of file ringsSkyMap.py.

    def __init__(self, config, version=1):
        assert version in (0, 1), "Unrecognised version: %s" % (version,)
        # We count rings from south to north
        # Note: pole caps together count for one additional ring when calculating the ring size
        self._ringSize = math.pi / (config.numRings + 1)  # Size of a ring in Declination (radians)
        self._ringNums = []  # Number of tracts for each ring
        for i in range(config.numRings):
            startDec = self._ringSize*(i + 0.5) - 0.5*math.pi
            stopDec = startDec + self._ringSize
            dec = min(math.fabs(startDec), math.fabs(stopDec))  # Declination for determining division in RA
            self._ringNums.append(int(2*math.pi*math.cos(dec)/self._ringSize) + 1)
        numTracts = sum(self._ringNums) + 2
        super(RingsSkyMap, self).__init__(numTracts, config, version)
        self._raStart = self.config.raStart*geom.degrees
 

Member Function Documentation

__eq__()

def lsst.skymap.baseSkyMap.BaseSkyMap.__eq__ (   self,   other  )

inherited

Definition at line 212 of file baseSkyMap.py.

    def __eq__(self, other):
        try:
            return self.getSha1() == other.getSha1()
        except AttributeError:
            return NotImplemented
 

__getitem__()

def lsst.skymap.cachingSkyMap.CachingSkyMap.__getitem__ (   self,   index  )

inherited

Get the TractInfo for a particular index.

The tract is returned from a cache, if available, otherwise generated
on the fly.

Reimplemented from lsst.skymap.baseSkyMap.BaseSkyMap.

Definition at line 80 of file cachingSkyMap.py.

    def __getitem__(self, index):
        """Get the TractInfo for a particular index.
 
        The tract is returned from a cache, if available, otherwise generated
        on the fly.
        """
        if index < 0 or index > self._numTracts:
            raise IndexError("Index out of range: %d vs %d" % (index, self._numTracts))
        if self._tractCache[index] is not None:
            return self._tractCache[index]
        tract = self.generateTract(index)
        self._tractCache[index] = tract
        return tract
 

__hash__()

def lsst.skymap.baseSkyMap.BaseSkyMap.__hash__ (   self )

inherited

Definition at line 209 of file baseSkyMap.py.

    def __hash__(self):
        return hash(self.getSha1())
 

__iter__()

def lsst.skymap.cachingSkyMap.CachingSkyMap.__iter__ (   self )

inherited

Iterator over tracts.

Reimplemented from lsst.skymap.baseSkyMap.BaseSkyMap.

Definition at line 71 of file cachingSkyMap.py.

    def __iter__(self):
        """Iterator over tracts."""
        for i in range(self._numTracts):
            yield self[i]
 

__len__()

def lsst.skymap.cachingSkyMap.CachingSkyMap.__len__ (   self )

inherited

Length is number of tracts.

Reimplemented from lsst.skymap.baseSkyMap.BaseSkyMap.

Definition at line 76 of file cachingSkyMap.py.

    def __len__(self):
        """Length is number of tracts."""
        return self._numTracts
 

__ne__()

def lsst.skymap.baseSkyMap.BaseSkyMap.__ne__ (   self,   other  )

inherited

Definition at line 218 of file baseSkyMap.py.

    def __ne__(self, other):
        return not (self == other)
 

__reduce__()

def lsst.skymap.cachingSkyMap.CachingSkyMap.__reduce__ (   self )

inherited

To support pickling.

Notes
-----
**Warning:** This method assumes that the constructor is be defined:
    __init__(self, config, version=defaultVersion)
The use of 'config' is effectively set by the registry mechanism.
If additional optional arguments are added, this method should be
overridden to correspond.

Definition at line 58 of file cachingSkyMap.py.

    def __reduce__(self):
        """To support pickling.
 
        Notes
        -----
        **Warning:** This method assumes that the constructor is be defined:
            __init__(self, config, version=defaultVersion)
        The use of 'config' is effectively set by the registry mechanism.
        If additional optional arguments are added, this method should be
        overridden to correspond.
        """
        return (self.__class__, (self.config, self._version))
 

findAllTracts()

def lsst.skymap.ringsSkyMap.RingsSkyMap.findAllTracts	(		self,
			coord
	)

Find all tracts which include the specified coord.

Parameters
----------
coord : `lsst.geom.SpherePoint`
    ICRS sky coordinate to search for.

Returns
-------
tractList : `list` of `TractInfo`
    The tracts which include the specified coord.

Definition at line 204 of file ringsSkyMap.py.

    def findAllTracts(self, coord):
        """Find all tracts which include the specified coord.
 
        Parameters
        ----------
        coord : `lsst.geom.SpherePoint`
            ICRS sky coordinate to search for.
 
        Returns
        -------
        tractList : `list` of `TractInfo`
            The tracts which include the specified coord.
        """
        ringNum = self._decToRingNum(coord.getLatitude())
 
        tractList = list()
        # ringNum denotes the closest ring to the specified coord
        # I will check adjacent rings which may include the specified coord
        for r in [ringNum - 1, ringNum, ringNum + 1]:
            if r < 0 or r >= self.config.numRings:
                # Poles will be checked explicitly outside this loop
                continue
            tractNum = self._raToTractNum(coord.getLongitude(), r)
            # Adjacent tracts will also be checked.
            for t in [tractNum - 1, tractNum, tractNum + 1]:
                # Wrap over raStart
                if t < 0:
                    t = t + self._ringNums[r]
                elif t > self._ringNums[r] - 1:
                    t = t - self._ringNums[r]
 
                extra = 0
                if self._version == 0 and t == 0 and r != 0:
                    # Account for off-by-one error in getRingIndices
                    # Note that this means that tract 1 gets duplicated.
                    extra = 1
 
                index = sum(self._ringNums[:r + extra], t + 1)  # Allow 1 for south pole
                tract = self[index]
                if tract.contains(coord):
                    tractList.append(tract)
 
        # Always check tracts at poles
        # Southern cap is 0, Northern cap is the last entry in self
        for entry in [0, len(self)-1]:
            tract = self[entry]
            if tract.contains(coord):
                tractList.append(tract)
 
        return tractList
 

findClosestTractPatchList()

def lsst.skymap.baseSkyMap.BaseSkyMap.findClosestTractPatchList (   self,   coordList  )

inherited

Find closest tract and patches that overlap coordinates.

Parameters
----------
coordList : `lsst.geom.SpherePoint`
    List of ICRS sky coordinates to search for.

Returns
-------
retList : `list`
    list of (TractInfo, list of PatchInfo) for tracts and patches
    that contain, or may contain, the specified region.
    The list will be empty if there is no overlap.

Definition at line 177 of file baseSkyMap.py.

    def findClosestTractPatchList(self, coordList):
        """Find closest tract and patches that overlap coordinates.
 
        Parameters
        ----------
        coordList : `lsst.geom.SpherePoint`
            List of ICRS sky coordinates to search for.
 
        Returns
        -------
        retList : `list`
            list of (TractInfo, list of PatchInfo) for tracts and patches
            that contain, or may contain, the specified region.
            The list will be empty if there is no overlap.
        """
        retList = []
        for coord in coordList:
            tractInfo = self.findTract(coord)
            patchList = tractInfo.findPatchList(coordList)
            if patchList and not (tractInfo, patchList) in retList:
                retList.append((tractInfo, patchList))
        return retList
 

findTract()

def lsst.skymap.ringsSkyMap.RingsSkyMap.findTract	(		self,
			coord
	)

Find the tract whose center is nearest the specified coord.

Parameters
----------
coord : `lsst.geom.SpherePoint`
    ICRS sky coordinate to search for.

Returns
-------
result : `TractInfo`
    TractInfo of tract whose center is nearest the specified coord.

Notes
-----
- If coord is equidistant between multiple sky tract centers then one
  is arbitrarily chosen.

- The default implementation is not very efficient; subclasses may wish
  to override.

**Warning:**
If tracts do not cover the whole sky then the returned tract may not
include the coord.

Reimplemented from lsst.skymap.baseSkyMap.BaseSkyMap.

Definition at line 186 of file ringsSkyMap.py.

    def findTract(self, coord):
        ringNum = self._decToRingNum(coord.getLatitude())
        if ringNum == -1:
            # Southern cap
            return self[0]
        if ringNum == self.config.numRings:
            # Northern cap
            return self[self._numTracts - 1]
        tractNum = self._raToTractNum(coord.getLongitude(), ringNum)
 
        if self._version == 0 and tractNum == 0 and ringNum != 0:
            # Account for off-by-one error in getRingIndices
            # Note that this means that tract 1 gets duplicated.
            ringNum += 1
 
        index = sum(self._ringNums[:ringNum], tractNum + 1)  # Allow 1 for south pole
        return self[index]
 

findTractPatchList()

def lsst.skymap.ringsSkyMap.RingsSkyMap.findTractPatchList	(		self,
			coordList
	)

Find tracts and patches that overlap a region.

Parameters
----------
coordList : `list` of `lsst.geom.SpherePoint`
    List of ICRS sky coordinates to search for.

Returns
-------
reList : `list` of (`TractInfo`, `list` of `PatchInfo`)
    For tracts and patches that contain, or may contain, the specified
    region. The list will be empty if there is no overlap.

Notes
-----
**warning:**
    This uses a naive algorithm that may find some tracts and patches
    that do not overlap the region (especially if the region is not a
    rectangle aligned along patch x, y).

Reimplemented from lsst.skymap.baseSkyMap.BaseSkyMap.

Definition at line 255 of file ringsSkyMap.py.

    def findTractPatchList(self, coordList):
        retList = []
        for coord in coordList:
            for tractInfo in self.findAllTracts(coord):
                patchList = tractInfo.findPatchList(coordList)
                if patchList and not (tractInfo, patchList) in retList:
                    retList.append((tractInfo, patchList))
        return retList
 

generateTract()

def lsst.skymap.ringsSkyMap.RingsSkyMap.generateTract	(		self,
			index
	)

Generate TractInfo for the specified tract index.

Reimplemented from lsst.skymap.cachingSkyMap.CachingSkyMap.

Definition at line 123 of file ringsSkyMap.py.

    def generateTract(self, index):
        """Generate TractInfo for the specified tract index."""
        ringNum, tractNum = self.getRingIndices(index)
        if ringNum == -1:  # South polar cap
            ra, dec = 0, -0.5*math.pi
        elif ringNum == self.config.numRings:  # North polar cap
            ra, dec = 0, 0.5*math.pi
        else:
            dec = self._ringSize*(ringNum + 1) - 0.5*math.pi
            ra = ((2*math.pi*tractNum/self._ringNums[ringNum])*geom.radians
                  + self._raStart).wrap().asRadians()
 
        center = geom.SpherePoint(ra, dec, geom.radians)
        wcs = self._wcsFactory.makeWcs(crPixPos=geom.Point2D(0, 0), crValCoord=center)
        return ExplicitTractInfo(index, self.config.patchInnerDimensions, self.config.patchBorder, center,
                                 0.5*self._ringSize*geom.radians, self.config.tractOverlap*geom.degrees,
                                 wcs)
 

getRingIndices()

def lsst.skymap.ringsSkyMap.RingsSkyMap.getRingIndices	(		self,
			index
	)

Calculate ring indices given a numerical index of a tract.

The ring indices are the ring number and the tract number within
the ring.

The ring number is -1 for the south polar cap and increases to the
north.  The north polar cap has ring number = numRings.  The tract
number is zero for either of the polar caps.

Definition at line 92 of file ringsSkyMap.py.

    def getRingIndices(self, index):
        """Calculate ring indices given a numerical index of a tract.
 
        The ring indices are the ring number and the tract number within
        the ring.
 
        The ring number is -1 for the south polar cap and increases to the
        north.  The north polar cap has ring number = numRings.  The tract
        number is zero for either of the polar caps.
        """
        if index == 0:  # South polar cap
            return -1, 0
        if index == self._numTracts - 1:  # North polar cap
            return self.config.numRings, 0
        if index < 0 or index >= self._numTracts:
            raise IndexError("Tract index %d is out of range [0, %d]" % (index, len(self) - 1))
        ring = 0  # Ring number
        tractNum = index - 1  # Tract number within ring
        if self._version == 0:
            # Maintain the off-by-one bug in version=0 (DM-14809).
            # This means that the first tract in the first ring is duplicated
            # and the first tract in the last ring is missing.
            while ring < self.config.numRings and tractNum > self._ringNums[ring]:
                tractNum -= self._ringNums[ring]
                ring += 1
        else:
            while ring < self.config.numRings and tractNum >= self._ringNums[ring]:
                tractNum -= self._ringNums[ring]
                ring += 1
        return ring, tractNum
 

getSha1()

def lsst.skymap.baseSkyMap.BaseSkyMap.getSha1 (   self )

inherited

Return a SHA1 hash that uniquely identifies this SkyMap instance.

Returns
-------
sha1 : `bytes`
    A 20-byte hash that uniquely identifies this SkyMap instance.

Notes
-----
Subclasses should almost always override ``updateSha1`` instead of
this function to add subclass-specific state to the hash.

Definition at line 245 of file baseSkyMap.py.

    def getSha1(self):
        """Return a SHA1 hash that uniquely identifies this SkyMap instance.
 
        Returns
        -------
        sha1 : `bytes`
            A 20-byte hash that uniquely identifies this SkyMap instance.
 
        Notes
        -----
        Subclasses should almost always override ``updateSha1`` instead of
        this function to add subclass-specific state to the hash.
        """
        if self._sha1 is None:
            sha1 = hashlib.sha1()
            sha1.update(type(self).__name__.encode('utf-8'))
            configPacked = struct.pack(
                "<iiidd3sd",
                self.config.patchInnerDimensions[0],
                self.config.patchInnerDimensions[1],
                self.config.patchBorder,
                self.config.tractOverlap,
                self.config.pixelScale,
                self.config.projection.encode('ascii'),
                self.config.rotation
            )
            sha1.update(configPacked)
            self.updateSha1(sha1)
            self._sha1 = sha1.digest()
        return self._sha1
 

logSkyMapInfo()

def lsst.skymap.baseSkyMap.BaseSkyMap.logSkyMapInfo (   self,   log  )

inherited

Write information about a sky map to supplied log

Parameters
----------
log : `lsst.log.Log`
    Log object that information about skymap will be written

Definition at line 221 of file baseSkyMap.py.

    def logSkyMapInfo(self, log):
        """Write information about a sky map to supplied log
 
        Parameters
        ----------
        log : `lsst.log.Log`
            Log object that information about skymap will be written
        """
        log.info("sky map has %s tracts" % (len(self),))
        for tractInfo in self:
            wcs = tractInfo.getWcs()
            posBox = geom.Box2D(tractInfo.getBBox())
            pixelPosList = (
                posBox.getMin(),
                geom.Point2D(posBox.getMaxX(), posBox.getMinY()),
                posBox.getMax(),
                geom.Point2D(posBox.getMinX(), posBox.getMaxY()),
            )
            skyPosList = [wcs.pixelToSky(pos).getPosition(geom.degrees) for pos in pixelPosList]
            posStrList = ["(%0.3f, %0.3f)" % tuple(skyPos) for skyPos in skyPosList]
            log.info("tract %s has corners %s (RA, Dec deg) and %s x %s patches" %
                     (tractInfo.getId(), ", ".join(posStrList),
                      tractInfo.getNumPatches()[0], tractInfo.getNumPatches()[1]))
 

register()

def lsst.skymap.baseSkyMap.BaseSkyMap.register (   self,   name,   registry  )

inherited

Add SkyMap, Tract, and Patch Dimension entries to the given Gen3
Butler Registry.

Parameters
----------
name : `str`
    The name of the skymap.
registry : `lsst.daf.butler.Registry`
    The registry to add to.

Definition at line 293 of file baseSkyMap.py.

    def register(self, name, registry):
        """Add SkyMap, Tract, and Patch Dimension entries to the given Gen3
        Butler Registry.
 
        Parameters
        ----------
        name : `str`
            The name of the skymap.
        registry : `lsst.daf.butler.Registry`
            The registry to add to.
        """
        nxMax = 0
        nyMax = 0
        records = {
            "skymap": [],
            "tract": [],
            "patch": [],
        }
        for tractInfo in self:
            nx, ny = tractInfo.getNumPatches()
            nxMax = max(nxMax, nx)
            nyMax = max(nyMax, ny)
            region = tractInfo.getOuterSkyPolygon()
            centroid = SpherePoint(region.getCentroid())
            records["tract"].append({
                "skymap": name,
                "tract": tractInfo.getId(),
                "region": region,
                "ra": centroid.getRa().asDegrees(),
                "dec": centroid.getDec().asDegrees(),
            })
            for patchInfo in tractInfo:
                cellX, cellY = patchInfo.getIndex()
                records["patch"].append({
                    "skymap": name,
                    "tract": tractInfo.getId(),
                    "patch": tractInfo.getSequentialPatchIndex(patchInfo),
                    "cell_x": cellX,
                    "cell_y": cellY,
                    "region": patchInfo.getOuterSkyPolygon(tractInfo.getWcs()),
                })
        records["skymap"].append({
            "skymap": name,
            "hash": self.getSha1(),
            "tract_max": len(self),
            "patch_nx_max": nxMax,
            "patch_ny_max": nyMax,
        })
        with registry.transaction():
            for dimension, recordsForDimension in records.items():
                registry.insertDimensionData(dimension, *recordsForDimension)

updateSha1()

def lsst.skymap.ringsSkyMap.RingsSkyMap.updateSha1	(		self,
			sha1
	)

Add subclass-specific state or configuration options to the SHA1.

Reimplemented from lsst.skymap.baseSkyMap.BaseSkyMap.

Definition at line 264 of file ringsSkyMap.py.

    def updateSha1(self, sha1):
        """Add subclass-specific state or configuration options to the SHA1."""
        sha1.update(struct.pack("<id", self.config.numRings, self.config.raStart))

Member Data Documentation

config

lsst.skymap.baseSkyMap.BaseSkyMap.config

inherited

Definition at line 107 of file baseSkyMap.py.

ConfigClass

lsst.skymap.ringsSkyMap.RingsSkyMap.ConfigClass

static

Definition at line 74 of file ringsSkyMap.py.

---

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

• /j/snowflake/release/lsstsw/stack/1a1d771/Linux64/skymap/20.0.0/python/lsst/skymap/ringsSkyMap.py