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    *
    *   http://www.apache.org/licenses/LICENSE-2.0
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   * Unless required by applicable law or agreed to in writing, software
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  package org.orekit.models.earth.troposphere;
  
  import org.hipparchus.util.FastMath;
  import org.hipparchus.util.Precision;
  import org.junit.Assert;
  import org.junit.Before;
  import org.junit.BeforeClass;
  import org.junit.Test;
  import org.orekit.Utils;
  import org.orekit.bodies.GeodeticPoint;
  import org.orekit.errors.OrekitException;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.time.TimeScalesFactory;
  
  public class GlobalMappingFunctionModelTest {
  
      @BeforeClass
      public static void setUpGlobal() {
          Utils.setDataRoot("atmosphere");
      }
  
      @Before
      public void setUp() throws OrekitException {
          Utils.setDataRoot("regular-data:potential/shm-format");
      }
  
      @Test
      public void testMappingFactors() {
          
          // Site (NRAO, Green Bank, WV): latitude:  0.6708665767 radians
          //                              longitude: -1.393397187 radians
          //                              height:    844.715 m
          //
          // Date: MJD 55055 -> 12 August 2009 at 0h UT
          //
          // Ref:    Petit, G. and Luzum, B. (eds.), IERS Conventions (2010),
          //         IERS Technical Note No. 36, BKG (2010)
          //
          // Expected mapping factors : hydrostatic -> 3.425246 (Ref)
          //                                    wet -> 3.449589 (Ref)
  
          final AbsoluteDate date = AbsoluteDate.createMJDDate(55055, 0, TimeScalesFactory.getUTC());
          
          final double latitude    = 0.6708665767;
          final double longitude   = -1.393397187;
          final double height      = 844.715;
          final GeodeticPoint point = new GeodeticPoint(latitude, longitude, height);
  
          final double elevation     = 0.5 * FastMath.PI - 1.278564131;
          final double expectedHydro = 3.425246;
          final double expectedWet   = 3.449589;
  
          final MappingFunction model = new GlobalMappingFunctionModel();
          
          final double[] computedMapping = model.mappingFactors(elevation, point, date);
          
          Assert.assertEquals(expectedHydro, computedMapping[0], 1.0e-6);
          Assert.assertEquals(expectedWet,   computedMapping[1], 1.0e-6);
      }
  
      @Test
      public void testFixedHeight() {
          final AbsoluteDate date = new AbsoluteDate();
          MappingFunction model = new GlobalMappingFunctionModel();
          double[] lastFactors = new double[] {
              Double.MAX_VALUE,
              Double.MAX_VALUE
          };
          GeodeticPoint point = new GeodeticPoint(FastMath.toRadians(45.0), FastMath.toRadians(45.0), 350.0);
          // mapping functions shall decline with increasing elevation angle
          for (double elev = 10d; elev < 90d; elev += 8d) {
              final double[] factors = model.mappingFactors(FastMath.toRadians(elev), point, date);
              Assert.assertTrue(Precision.compareTo(factors[0], lastFactors[0], 1.0e-6) < 0);
              Assert.assertTrue(Precision.compareTo(factors[1], lastFactors[1], 1.0e-6) < 0);
              lastFactors[0] = factors[0];
              lastFactors[1] = factors[1];
          }
      }
  
  }