def test_regression_simple_5133():
"""
Simple test to check if alt-az calculations respect height of observer
Because ITRS is geocentric and includes aberration, an object that
appears 'straight up' to a geocentric observer (ITRS) won't be
straight up to a topocentric observer - see
https://github.com/astropy/astropy/issues/10983
This is why we construct a topocentric GCRS SkyCoord before calculating AltAz
"""
t = Time('J2010')
obj = EarthLocation(-1 * u.deg, 52 * u.deg, height=[10., 0.] * u.km)
home = EarthLocation(-1 * u.deg, 52 * u.deg, height=5. * u.km)
obsloc_gcrs, obsvel_gcrs = home.get_gcrs_posvel(t)
gcrs_geo = obj.get_itrs(t).transform_to(GCRS(obstime=t))
obsrepr = home.get_itrs(t).transform_to(GCRS(obstime=t)).cartesian
topo_gcrs_repr = gcrs_geo.cartesian - obsrepr
topocentric_gcrs_frame = GCRS(obstime=t,
obsgeoloc=obsloc_gcrs,
obsgeovel=obsvel_gcrs)
gcrs_topo = topocentric_gcrs_frame.realize_frame(topo_gcrs_repr)
aa = gcrs_topo.transform_to(AltAz(obstime=t, location=home))
# az is more-or-less undefined for straight up or down
assert_quantity_allclose(aa.alt, [90, -90] * u.deg, rtol=1e-7)
assert_quantity_allclose(aa.distance, 5 * u.km)
def test_gcrs_itrs():
"""
Check basic GCRS<->ITRS transforms for round-tripping.
"""
ra, dec, _ = randomly_sample_sphere(200)
gcrs = GCRS(ra=ra, dec=dec, obstime='J2000')
gcrs6 = GCRS(ra=ra, dec=dec, obstime='J2006')
gcrs2 = gcrs.transform_to(ITRS).transform_to(gcrs)
gcrs6_2 = gcrs6.transform_to(ITRS).transform_to(gcrs)
assert_allclose(gcrs.ra, gcrs2.ra)
assert_allclose(gcrs.dec, gcrs2.dec)
assert not allclose(gcrs.ra, gcrs6_2.ra)
assert not allclose(gcrs.dec, gcrs6_2.dec)
# also try with the cartesian representation
gcrsc = gcrs.realize_frame(gcrs.data)
gcrsc.representation_type = CartesianRepresentation
gcrsc2 = gcrsc.transform_to(ITRS).transform_to(gcrsc)
assert_allclose(gcrsc.spherical.lon.deg, gcrsc2.ra.deg)
assert_allclose(gcrsc.spherical.lat, gcrsc2.dec)
def test_gcrs_itrs():
"""
Check basic GCRS<->ITRS transforms for round-tripping.
"""
ra, dec, _ = randomly_sample_sphere(200)
gcrs = GCRS(ra=ra, dec=dec, obstime='J2000')
gcrs6 = GCRS(ra=ra, dec=dec, obstime='J2006')
gcrs2 = gcrs.transform_to(ITRS).transform_to(gcrs)
gcrs6_2 = gcrs6.transform_to(ITRS).transform_to(gcrs)
assert_allclose(gcrs.ra, gcrs2.ra)
assert_allclose(gcrs.dec, gcrs2.dec)
assert not allclose(gcrs.ra, gcrs6_2.ra)
assert not allclose(gcrs.dec, gcrs6_2.dec)
# also try with the cartesian representation
gcrsc = gcrs.realize_frame(gcrs.data)
gcrsc.representation_type = CartesianRepresentation
gcrsc2 = gcrsc.transform_to(ITRS).transform_to(gcrsc)
assert_allclose(gcrsc.spherical.lon.deg, gcrsc2.ra.deg)
assert_allclose(gcrsc.spherical.lat, gcrsc2.dec)
def test_gcrs_itrs():
"""
Check basic GCRS<->ITRS transforms for round-tripping.
"""
usph = golden_spiral_grid(200)
gcrs = GCRS(usph, obstime='J2000')
gcrs6 = GCRS(usph, obstime='J2006')
gcrs2 = gcrs.transform_to(ITRS()).transform_to(gcrs)
gcrs6_2 = gcrs6.transform_to(ITRS()).transform_to(gcrs)
assert_allclose(gcrs.ra, gcrs2.ra)
assert_allclose(gcrs.dec, gcrs2.dec)
# these should be different:
assert not allclose(gcrs.ra, gcrs6_2.ra, rtol=1e-8)
assert not allclose(gcrs.dec, gcrs6_2.dec, rtol=1e-8)
# also try with the cartesian representation
gcrsc = gcrs.realize_frame(gcrs.data)
gcrsc.representation_type = CartesianRepresentation
gcrsc2 = gcrsc.transform_to(ITRS()).transform_to(gcrsc)
assert_allclose(gcrsc.spherical.lon, gcrsc2.ra)
assert_allclose(gcrsc.spherical.lat, gcrsc2.dec)
