pytroll · mraspaud · Sep 26, 2019 · Sep 25, 2019 · Sep 25, 2019 · Sep 26, 2019
diff --git a/pygac/__init__.py b/pygac/__init__.py
@@ -33,5 +33,15 @@
     CONFIG_FILE = ''
 
 if not os.path.exists(CONFIG_FILE) or not os.path.isfile(CONFIG_FILE):
-    LOG.warning(str(CONFIG_FILE) + " pointed to by the environment "
-                + "variable PYGAC_CONFIG_FILE is not a file or does not exist!")
+    LOG.warning(
+        str(CONFIG_FILE) + " pointed to by the environment "
+        + "variable PYGAC_CONFIG_FILE is not a file or does not exist!")
+
+
+def get_absolute_azimuth_angle_diff(sat_azi, sun_azi):
+    """Calculates absolute azimuth difference angle. """
+    rel_azi = abs(sat_azi - sun_azi)
+    rel_azi = rel_azi % 360
+    # Not using np.where to avoid copying array
+    rel_azi[rel_azi > 180] = 360.0 - rel_azi[rel_azi > 180]
+    return rel_azi
diff --git a/pygac/gac_io.py b/pygac/gac_io.py
@@ -118,10 +118,6 @@ def save_gac(satellite_name,
     lons = np.where(np.logical_or(lons < -180.00, lons > 180.00),
                     MISSING_DATA_LATLON, lons)
 
-    sat_azi -= 180.0
-    rel_azi = abs(rel_azi)
-    rel_azi = 180.0 - rel_azi
-
     for array in [bt3, bt4, bt5]:
         array[array != MISSING_DATA] = 100 * array[array != MISSING_DATA]
         array[mask] = MISSING_DATA

diff --git a/pygac/gac_reader.py b/pygac/gac_reader.py
@@ -24,7 +24,7 @@
 specific read functions.
 """
 import numpy as np
-from pygac import CONFIG_FILE
+from pygac import CONFIG_FILE, get_absolute_azimuth_angle_diff
 try:
     import ConfigParser
 except ImportError:
@@ -364,11 +364,7 @@ def get_angles(self):
                                             self.lons, self.lats)
         del alt
         sun_azi = np.rad2deg(sun_azi)
-        sun_azi = np.where(sun_azi < 0, sun_azi + 180, sun_azi - 180)
-
-        rel_azi = abs(sat_azi - sun_azi)
-        rel_azi = np.where(rel_azi > 180.0, 360.0 - rel_azi, rel_azi)
-
+        rel_azi = get_absolute_azimuth_angle_diff(sun_azi, sat_azi)
         return sat_azi, sat_zenith, sun_azi, sun_zenith, rel_azi
 
     def correct_times_median(self, year, jday, msec):

diff --git a/pygac/tests/__init__.py b/pygac/tests/__init__.py
@@ -23,8 +23,9 @@
 """The tests package.
 """
 
-from pygac.tests import test_calibrate_pod, test_slerp, test_calibrate_klm, \
-    test_pod, test_corrections, test_reader, test_io
+from pygac.tests import (test_calibrate_pod, test_slerp, test_calibrate_klm,
+                         test_pod, test_corrections, test_reader, test_io,
+                         test_angles)
 import unittest
 
 
@@ -33,7 +34,7 @@ def suite():
     """
     mysuite = unittest.TestSuite()
     tests = (test_slerp, test_calibrate_klm, test_calibrate_pod,
-             test_pod, test_corrections, test_reader, test_io)
+             test_pod, test_corrections, test_reader, test_io, test_angles)
     for test in tests:
         mysuite.addTests(test.suite())
 

diff --git a/pygac/tests/test_angles.py b/pygac/tests/test_angles.py
@@ -0,0 +1,68 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+
+# Copyright (c) 2014-2019 Pytroll Developers
+
+# Author(s):
+
+#   Nina Hakansson <nina.hakansson@smhi.se>
+#   Adam Dybbroe <adam.dypbroe@smhi.se>
+
+# 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 GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Test function for the angle calculation."""
+
+import unittest
+
+import numpy as np
+
+from pygac import get_absolute_azimuth_angle_diff
+
+
+class TestAngles(unittest.TestCase):
+    """Test function for the angle calculation."""
+
+    def test_azidiff_angle(self):
+        """Test function for the azidiff angle."""
+        sat_az = np.ma.array([[48.0,  56.0, 64.0,  72.0],
+                              [80.0,  88.0, 96.0, 104.0],
+                              [-80.0,  -88.0, -96.0, -104.0],
+                              [-180.0,  -188.0, -196.0, -204.0]], mask=False)
+        sun_az = np.ma.array([[148.0,  156.0, 164.0,  172.0],
+                              [180.0,  188.0, 196.0, 204.0],
+                              [180.0,  188.0, 196.0, 204.0],
+                              [185.0,  193.0, 201.0, 209.0]], mask=False)
+
+        res = np.ma.array([[100., 100., 100., 100.],
+                           [100., 100., 100., 100.],
+                           [100.,  84.,  68.,  52.],
+                           [5.,  21.,  37.,  53.]],
+                          mask=False)
+        rel_azi = get_absolute_azimuth_angle_diff(sat_az, sun_az)
+
+        np.testing.assert_allclose(rel_azi, res)
+
+
+def suite():
+    """The suite for test_slerp
+    """
+    loader = unittest.TestLoader()
+    mysuite = unittest.TestSuite()
+    mysuite.addTest(loader.loadTestsFromTestCase(TestAngles))
+
+    return mysuite
+
+
+if __name__ == '__main__':
+    unittest.main()