code: /*******************************************************************************
   * Copyright (c) 2017 Attila Kovacs <attila[AT]sigmyne.com>.
   * All rights reserved. 
   * 
   * This file is part of crush.
   * 
   *     crush 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.
   * 
   *     crush 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 crush.  If not, see <http://www.gnu.org/licenses/>.
   * 
   * Contributors:
   *     Attila Kovacs <attila[AT]sigmyne.com> - initial API and implementation
   ******************************************************************************/
  
  package crush.telescope.sofia;
  
  
  import java.util.List;
  
  import jnum.Configurator;
  import jnum.Unit;
  
  public class AtranModel {
      private List<Double> amCoeffs;
      private List<Double> altCoeffs;
    
      private double referenceTransmission = 1.0;
      
      public AtranModel(Configurator options) {
          init(options);
      }
      
      private void init(Configurator options) throws IllegalStateException {
          if(options.hasOption("atran.amcoeffs")) amCoeffs = options.option("atran.amcoeffs").getDoubles();
          else throw new IllegalStateException("Undefined option 'atran.amcoeffs'");
          
          if(options.hasOption("atran.altcoeffs")) altCoeffs = options.option("atran.altcoeffs").getDoubles();
          else throw new IllegalStateException("Undefined option 'atran.altcoeffs'");
          
          if(options.hasOption("atran.reference")) referenceTransmission = options.option("atran.reference").getDouble();
      }
      
      public double getReferenceTransmission() { return referenceTransmission; }
      
      public double getRelativeTransmission(double altitude, double elevation) {
          return getValueAt(1.0 / Math.sin(elevation) - referenceAirmass, amCoeffs) * 
                  getValueAt((altitude - referenceAltitude) / kft, altCoeffs);
      }
      
     
      private double getValueAt(double dx, List<Double> coeffs) {
          double value = 0.0;
          double term = 1.0;
          
          for(int i=0; i<coeffs.size(); i++) {
              value += coeffs.get(i) * term;
              term *= dx;
          }
        
          return value;
      }
      
      private final double kft = 1000.0 * Unit.ft;
      private final double referenceAirmass = Math.sqrt(2.0);
      private final double referenceAltitude = 41.0 * kft;
  }
  