def scale(self):
if self.meta['cunit2'] == 'Sine Latitude':
# Since, this map uses the cylindrical equal-area (CEA) projection,
# the spacing should be modified to 180/pi times the original value
# Reference: Section 5.5, Thompson 2006
return SpatialPair(np.abs(self.meta['cdelt1']) * self.spatial_units[0] / u.pixel,
180 / np.pi * self.meta['cdelt2'] * u.deg / u.pixel)
def spatial_units(self):
cunit1 = self.meta['cunit1']
if cunit1 == 'Degree':
cunit1 = 'deg'
cunit2 = self.meta['cunit2']
if cunit2 == 'Sine Latitude':
cunit2 = 'deg'
return SpatialPair(u.Unit(cunit1), u.Unit(cunit2))
def coordinate_system(self):
"""
If CTYPE{1 or 2} are equal to 'arcsec', assumes that CTYPE{1 or 2}
respectively are intended to be 'HPLN-TAN' or 'HPLT-TAN'.
"""
ctype1, ctype2 = self.meta['ctype1'], self.meta['ctype2']
if ctype1 == 'arcsec':
ctype1 = 'HPLN-TAN'
if ctype2 == 'arcsec':
ctype2 = 'HPLT-TAN'
return SpatialPair(ctype1, ctype2)
def spatial_units(self):
"""
If CTYPE{1 or 2} are equal to 'arcsec', assumes that CTYPE{1 or 2}
respectively are intended to be 'arcsec'.
"""
units = [self.meta.get('cunit1', None), self.meta.get('cunit2', None)]
if self.meta['ctype1'] == 'arcsec':
units[0] = 'arcsec'
if self.meta['ctype2'] == 'arcsec':
units[1] = 'arcsec'
units = [None if unit is None else u.Unit(unit.lower()) for unit in units]
return SpatialPair(units[0], units[1])
def spatial_units(self):
"""
If not present in CUNIT{1,2} keywords, defaults to arcsec.
"""
return SpatialPair(u.Unit(self.meta.get('cunit1', 'arcsec')),
u.Unit(self.meta.get('cunit2', 'arcsec')))
def spatial_units(self):
return SpatialPair(u.Unit(self.meta.get('cunit1').lower()),
u.Unit(self.meta.get('cunit2').lower()))
