fix coordinate transform issue

fftvis/simulate.py

@@ -251,6 +251,7 @@ def simulate(
 
     # Rotate the array to the xy-plane
     rotation_matrix = utils.get_plane_to_xy_rotation_matrix(antvecs)
+    rotation_matrix = rotation_matrix.astype(real_dtype)
     rotated_antvecs = np.dot(rotation_matrix.T, antvecs.T)
     rotated_ants = {ant: rotated_antvecs[:, antkey_to_idx[ant]] for ant in ants}
 
@@ -304,9 +305,6 @@ def simulate(
             ty = ty[above_horizon]
             tz = tz[above_horizon]
 
-            # Rotate source coordinates with rotation matrix
-            tx, ty, tz = np.dot(rotation_matrix.T, [tx, ty, tz])
-
             # Number of above horizon points
             nsim_sources = above_horizon.sum()
 
@@ -324,6 +322,9 @@ def simulate(
             # Compute azimuth and zenith angles
             az, za = conversions.enu_to_az_za(enu_e=tx, enu_n=ty, orientation="uvbeam")
 
+            # Rotate source coordinates with rotation matrix.
+            tx, ty, tz = np.dot(rotation_matrix.T, [tx, ty, tz])
+
             for fi in range(nfreqs):
                 # Compute uv coordinates
                 u[:], v[:], w[:] = blx * freqs[fi], bly * freqs[fi], blz * freqs[fi]

fftvis/tests/test_compare_matvis.py

@@ -138,6 +138,7 @@ def test_simulate_non_coplanar():
 
     # Set up the antenna positions
     antpos = {k: np.array([k * 10, 0, k]) for k in range(nants)}
+    antpos_flat = {k: np.array([k * 10, 0, 0]) for k in range(nants)}
 
     # Define a Gaussian beam
     beam = AnalyticBeam("gaussian", diameter=14.0)
@@ -151,6 +152,9 @@ def test_simulate_non_coplanar():
     mvis = matvis.simulate_vis(
         antpos, sky_model, ra, dec, freqs, lsts, beams=[beam], precision=2
     )
+    mvis_flat = matvis.simulate_vis(
+        antpos_flat, sky_model, ra, dec, freqs, lsts, beams=[beam], precision=2
+    )
 
     # Use fftvis to simulate visibilities
     fvis = simulate.simulate_vis(
@@ -160,10 +164,5 @@ def test_simulate_non_coplanar():
     # Check that the results are the same
     assert np.allclose(mvis, fvis, atol=1e-5)
 
-    # Use fftvis to simulate visibilities with flat array
-    fvis_flat = simulate.simulate_vis(
-        antpos, sky_model, ra, dec, freqs, lsts, beam, precision=2, eps=1e-10, flat_array_tol=np.inf
-    )
-
     # Check that the results are different
-    assert not np.allclose(fvis, fvis_flat, atol=1e-5)
+    assert not np.allclose(mvis_flat, fvis, atol=1e-5)