dodecaSkyMap.py

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# 
# LSST Data Management System
# Copyright 2008, 2009, 2010 LSST Corporation.
# 
# This product includes software developed by the
# LSST Project (http://www.lsst.org/).
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# 
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# 
# You should have received a copy of the LSST License Statement and 
# the GNU General Public License along with this program.  If not, 
# see <http://www.lsstcorp.org/LegalNotices/>.
#
"""
@todo
- Consider tweaking pixel scale so the average scale is as specified, rather than the scale at the center
"""
import lsst.pex.config as pexConfig
import lsst.afw.geom as afwGeom
from . import detail
from .baseSkyMap import BaseSkyMap
from .tractInfo import TractInfo

class DodecaSkyMapConfig(BaseSkyMap.ConfigClass):
    withTractsOnPoles = pexConfig.Field(
        doc = "if True center a tract on each pole, else put a vertex on each pole",
        dtype = bool,
        default = False,
    )

    def setDefaults(self):
        self.tractOverlap = 3.5
        self.patchBorder = 250
        self.pixelScale = 10.0 / 50.0 # LSST plate scale is 50 um/arcsec and pixel size is 10 um
        self.patchInnerDimensions = (4000, 4000)
        self.projection = "STG"


class DodecaSkyMap(BaseSkyMap):
    """Dodecahedron-based sky map pixelization.
        
    DodecaSkyMap divides the sky into 12 overlapping Tracts arranged as the faces of a dodecahedron.
    """
    ConfigClass = DodecaSkyMapConfig
    _version = (1, 0) # for pickle

    def __init__(self, config=None):
        """Construct a DodecaSkyMap

        @param[in] config: an instance of self.ConfigClass; if None the default config is used
        """
        BaseSkyMap.__init__(self, config)
        self._dodecahedron = detail.Dodecahedron(withFacesOnPoles = self.config.withTractsOnPoles)
        
        tractOverlap = afwGeom.Angle(self.config.tractOverlap, afwGeom.degrees)

        for id in range(12):
            tractVec = self._dodecahedron.getFaceCtr(id)
            tractCoord = detail.coordFromVec(tractVec, defRA=afwGeom.Angle(0))
            tractRA = tractCoord.getLongitude()
            vertexVecList = self._dodecahedron.getVertices(id)
            
            # make initial WCS; don't worry about crPixPos because TractInfo will shift it as required
            wcs = self._wcsFactory.makeWcs(crPixPos=afwGeom.Point2D(0,0), crValCoord=tractCoord)
            
            self._tractInfoList.append(
                TractInfo(
                    id = id,
                    patchInnerDimensions = self.config.patchInnerDimensions,
                    patchBorder = self.config.patchBorder,
                    ctrCoord = tractCoord,
                    vertexCoordList = [detail.coordFromVec(vec, defRA=tractRA) for vec in vertexVecList],
                    tractOverlap = tractOverlap,
                    wcs = wcs,
                )
            )
    
    def __getstate__(self):
        """Support pickle
        
        @return a dict containing:
        - version: a pair of ints
        - config: the config
        """
        return dict(
            version = self._version,
            config = self.config,
        )
    
    def __setstate__(self, stateDict):
        """Support unpickle
        
        @param[in] stateDict: a dict containing:
        - version: a pair of ints
        - config: the config
        """
        version = stateDict["version"]
        if version >= (2, 0):
            raise runtimeError("Version = %s >= (2,0); cannot unpickle" % (version,))
        self.__init__(stateDict["config"])
    
    def findTract(self, coord):
        """Find the tract whose inner region includes the coord.
        
        @param[in] coord: sky coordinate (afwCoord.Coord)
        @return TractInfo for tract whose inner region includes the coord.
        
        @note This routine will be more efficient if coord is ICRS.
        """
        return self[self._dodecahedron.getFaceInd(coord.toIcrs().getVector())]
    
    def getVersion(self):
        """Return version (e.g. for pickle)
        
        @return version as a pair of integers
        """
        return self._version
    
    def getWithTractsOnPoles(self):
        """Return withTractsOnPoles parameter
        
        @return withTractsOnPoles as a bool
        """
        return self._dodecahedron.getWithFacesOnPoles()