@cquiroz/aladin-lite/lib/js/CooConversion.js

AladinLite module

// Copyright 2013 - UDS/CNRS
// The Aladin Lite program is distributed under the terms
// of the GNU General Public License version 3.
//
// This file is part of Aladin Lite.
//
//    Aladin Lite 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, version 3 of the License.
//
//    Aladin Lite 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.
//
//    The GNU General Public License is available in COPYING file
//    along with Aladin Lite.
//
var CooConversion = function () {
  var CooConversion = {};
  CooConversion.GALACTIC_TO_J2000 = [-0.0548755604024359, 0.4941094279435681, -0.8676661489811610, -0.8734370902479237, -0.4448296299195045, -0.1980763734646737, -0.4838350155267381, 0.7469822444763707, 0.4559837762325372];
  CooConversion.J2000_TO_GALACTIC = [-0.0548755604024359, -0.873437090247923, -0.4838350155267381, 0.4941094279435681, -0.4448296299195045, 0.7469822444763707, -0.8676661489811610, -0.1980763734646737, 0.4559837762325372]; // adapted from www.robertmartinayers.org/tools/coordinates.html
  // radec : array of ra, dec in degrees
  // return coo in degrees

  CooConversion.Transform = function (radec, matrix) {
    // returns a radec array of two elements
    radec[0] = radec[0] * Math.PI / 180;
    radec[1] = radec[1] * Math.PI / 180;
    var r0 = [Math.cos(radec[0]) * Math.cos(radec[1]), Math.sin(radec[0]) * Math.cos(radec[1]), Math.sin(radec[1])];
    var s0 = [r0[0] * matrix[0] + r0[1] * matrix[1] + r0[2] * matrix[2], r0[0] * matrix[3] + r0[1] * matrix[4] + r0[2] * matrix[5], r0[0] * matrix[6] + r0[1] * matrix[7] + r0[2] * matrix[8]];
    var r = Math.sqrt(s0[0] * s0[0] + s0[1] * s0[1] + s0[2] * s0[2]);
    var result = [0.0, 0.0];
    result[1] = Math.asin(s0[2] / r); // New dec in range -90.0 -- +90.0
    // or use sin^2 + cos^2 = 1.0

    var cosaa = s0[0] / r / Math.cos(result[1]);
    var sinaa = s0[1] / r / Math.cos(result[1]);
    result[0] = Math.atan2(sinaa, cosaa);
    if (result[0] < 0.0) result[0] = result[0] + 2 * Math.PI;
    result[0] = result[0] * 180 / Math.PI;
    result[1] = result[1] * 180 / Math.PI;
    return result;
  }; // coo : array of lon, lat in degrees


  CooConversion.GalacticToJ2000 = function (coo) {
    return CooConversion.Transform(coo, CooConversion.GALACTIC_TO_J2000);
  }; // coo : array of lon, lat in degrees


  CooConversion.J2000ToGalactic = function (coo) {
    return CooConversion.Transform(coo, CooConversion.J2000_TO_GALACTIC);
  };

  return CooConversion;
}();

export default CooConversion;