wcslib (8.2.2)
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<a href="sph_8h.html">Go to the documentation of this file.</a><div class="fragment"><div class="line"><a id="l00001" name="l00001"></a><span class="lineno"> 1</span><span class="comment">/*============================================================================</span></div>
<div class="line"><a id="l00002" name="l00002"></a><span class="lineno"> 2</span><span class="comment"> WCSLIB 8.2 - an implementation of the FITS WCS standard.</span></div>
<div class="line"><a id="l00003" name="l00003"></a><span class="lineno"> 3</span><span class="comment"> Copyright (C) 1995-2023, Mark Calabretta</span></div>
<div class="line"><a id="l00004" name="l00004"></a><span class="lineno"> 4</span><span class="comment"></span> </div>
<div class="line"><a id="l00005" name="l00005"></a><span class="lineno"> 5</span><span class="comment"> This file is part of WCSLIB.</span></div>
<div class="line"><a id="l00006" name="l00006"></a><span class="lineno"> 6</span><span class="comment"></span> </div>
<div class="line"><a id="l00007" name="l00007"></a><span class="lineno"> 7</span><span class="comment"> WCSLIB is free software: you can redistribute it and/or modify it under the</span></div>
<div class="line"><a id="l00008" name="l00008"></a><span class="lineno"> 8</span><span class="comment"> terms of the GNU Lesser General Public License as published by the Free</span></div>
<div class="line"><a id="l00009" name="l00009"></a><span class="lineno"> 9</span><span class="comment"> Software Foundation, either version 3 of the License, or (at your option)</span></div>
<div class="line"><a id="l00010" name="l00010"></a><span class="lineno"> 10</span><span class="comment"> any later version.</span></div>
<div class="line"><a id="l00011" name="l00011"></a><span class="lineno"> 11</span><span class="comment"></span> </div>
<div class="line"><a id="l00012" name="l00012"></a><span class="lineno"> 12</span><span class="comment"> WCSLIB is distributed in the hope that it will be useful, but WITHOUT ANY</span></div>
<div class="line"><a id="l00013" name="l00013"></a><span class="lineno"> 13</span><span class="comment"> WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS</span></div>
<div class="line"><a id="l00014" name="l00014"></a><span class="lineno"> 14</span><span class="comment"> FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for</span></div>
<div class="line"><a id="l00015" name="l00015"></a><span class="lineno"> 15</span><span class="comment"> more details.</span></div>
<div class="line"><a id="l00016" name="l00016"></a><span class="lineno"> 16</span><span class="comment"></span> </div>
<div class="line"><a id="l00017" name="l00017"></a><span class="lineno"> 17</span><span class="comment"> You should have received a copy of the GNU Lesser General Public License</span></div>
<div class="line"><a id="l00018" name="l00018"></a><span class="lineno"> 18</span><span class="comment"> along with WCSLIB. If not, see http://www.gnu.org/licenses.</span></div>
<div class="line"><a id="l00019" name="l00019"></a><span class="lineno"> 19</span><span class="comment"></span> </div>
<div class="line"><a id="l00020" name="l00020"></a><span class="lineno"> 20</span><span class="comment"> Author: Mark Calabretta, Australia Telescope National Facility, CSIRO.</span></div>
<div class="line"><a id="l00021" name="l00021"></a><span class="lineno"> 21</span><span class="comment"> http://www.atnf.csiro.au/people/Mark.Calabretta</span></div>
<div class="line"><a id="l00022" name="l00022"></a><span class="lineno"> 22</span><span class="comment"> $Id: sph.h,v 8.2.1.1 2023/11/16 10:05:57 mcalabre Exp mcalabre $</span></div>
<div class="line"><a id="l00023" name="l00023"></a><span class="lineno"> 23</span><span class="comment">*=============================================================================</span></div>
<div class="line"><a id="l00024" name="l00024"></a><span class="lineno"> 24</span><span class="comment">*</span></div>
<div class="line"><a id="l00025" name="l00025"></a><span class="lineno"> 25</span><span class="comment">* WCSLIB 8.2 - C routines that implement the FITS World Coordinate System</span></div>
<div class="line"><a id="l00026" name="l00026"></a><span class="lineno"> 26</span><span class="comment">* (WCS) standard. Refer to the README file provided with WCSLIB for an</span></div>
<div class="line"><a id="l00027" name="l00027"></a><span class="lineno"> 27</span><span class="comment">* overview of the library.</span></div>
<div class="line"><a id="l00028" name="l00028"></a><span class="lineno"> 28</span><span class="comment">*</span></div>
<div class="line"><a id="l00029" name="l00029"></a><span class="lineno"> 29</span><span class="comment">*</span></div>
<div class="line"><a id="l00030" name="l00030"></a><span class="lineno"> 30</span><span class="comment">* Summary of the sph routines</span></div>
<div class="line"><a id="l00031" name="l00031"></a><span class="lineno"> 31</span><span class="comment">* ---------------------------</span></div>
<div class="line"><a id="l00032" name="l00032"></a><span class="lineno"> 32</span><span class="comment">* Routines in this suite implement the spherical coordinate transformations</span></div>
<div class="line"><a id="l00033" name="l00033"></a><span class="lineno"> 33</span><span class="comment">* defined by the FITS World Coordinate System (WCS) standard</span></div>
<div class="line"><a id="l00034" name="l00034"></a><span class="lineno"> 34</span><span class="comment">*</span></div>
<div class="line"><a id="l00035" name="l00035"></a><span class="lineno"> 35</span><span class="comment">= "Representations of world coordinates in FITS",</span></div>
<div class="line"><a id="l00036" name="l00036"></a><span class="lineno"> 36</span><span class="comment">= Greisen, E.W., & Calabretta, M.R. 2002, A&A, 395, 1061 (WCS Paper I)</span></div>
<div class="line"><a id="l00037" name="l00037"></a><span class="lineno"> 37</span><span class="comment">=</span></div>
<div class="line"><a id="l00038" name="l00038"></a><span class="lineno"> 38</span><span class="comment">= "Representations of celestial coordinates in FITS",</span></div>
<div class="line"><a id="l00039" name="l00039"></a><span class="lineno"> 39</span><span class="comment">= Calabretta, M.R., & Greisen, E.W. 2002, A&A, 395, 1077 (WCS Paper II)</span></div>
<div class="line"><a id="l00040" name="l00040"></a><span class="lineno"> 40</span><span class="comment">*</span></div>
<div class="line"><a id="l00041" name="l00041"></a><span class="lineno"> 41</span><span class="comment">* The transformations are implemented via separate functions, sphx2s() and</span></div>
<div class="line"><a id="l00042" name="l00042"></a><span class="lineno"> 42</span><span class="comment">* sphs2x(), for the spherical rotation in each direction.</span></div>
<div class="line"><a id="l00043" name="l00043"></a><span class="lineno"> 43</span><span class="comment">*</span></div>
<div class="line"><a id="l00044" name="l00044"></a><span class="lineno"> 44</span><span class="comment">* A utility function, sphdpa(), computes the angular distances and position</span></div>
<div class="line"><a id="l00045" name="l00045"></a><span class="lineno"> 45</span><span class="comment">* angles from a given point on the sky to a number of other points. sphpad()</span></div>
<div class="line"><a id="l00046" name="l00046"></a><span class="lineno"> 46</span><span class="comment">* does the complementary operation - computes the coordinates of points offset</span></div>
<div class="line"><a id="l00047" name="l00047"></a><span class="lineno"> 47</span><span class="comment">* by the given angular distances and position angles from a given point on the</span></div>
<div class="line"><a id="l00048" name="l00048"></a><span class="lineno"> 48</span><span class="comment">* sky.</span></div>
<div class="line"><a id="l00049" name="l00049"></a><span class="lineno"> 49</span><span class="comment">*</span></div>
<div class="line"><a id="l00050" name="l00050"></a><span class="lineno"> 50</span><span class="comment">*</span></div>
<div class="line"><a id="l00051" name="l00051"></a><span class="lineno"> 51</span><span class="comment">* sphx2s() - Rotation in the pixel-to-world direction</span></div>
<div class="line"><a id="l00052" name="l00052"></a><span class="lineno"> 52</span><span class="comment">* ---------------------------------------------------</span></div>
<div class="line"><a id="l00053" name="l00053"></a><span class="lineno"> 53</span><span class="comment">* sphx2s() transforms native coordinates of a projection to celestial</span></div>
<div class="line"><a id="l00054" name="l00054"></a><span class="lineno"> 54</span><span class="comment">* coordinates.</span></div>
<div class="line"><a id="l00055" name="l00055"></a><span class="lineno"> 55</span><span class="comment">*</span></div>
<div class="line"><a id="l00056" name="l00056"></a><span class="lineno"> 56</span><span class="comment">* Given:</span></div>
<div class="line"><a id="l00057" name="l00057"></a><span class="lineno"> 57</span><span class="comment">* eul const double[5]</span></div>
<div class="line"><a id="l00058" name="l00058"></a><span class="lineno"> 58</span><span class="comment">* Euler angles for the transformation:</span></div>
<div class="line"><a id="l00059" name="l00059"></a><span class="lineno"> 59</span><span class="comment">* 0: Celestial longitude of the native pole [deg].</span></div>
<div class="line"><a id="l00060" name="l00060"></a><span class="lineno"> 60</span><span class="comment">* 1: Celestial colatitude of the native pole, or</span></div>
<div class="line"><a id="l00061" name="l00061"></a><span class="lineno"> 61</span><span class="comment">* native colatitude of the celestial pole [deg].</span></div>
<div class="line"><a id="l00062" name="l00062"></a><span class="lineno"> 62</span><span class="comment">* 2: Native longitude of the celestial pole [deg].</span></div>
<div class="line"><a id="l00063" name="l00063"></a><span class="lineno"> 63</span><span class="comment">* 3: cos(eul[1])</span></div>
<div class="line"><a id="l00064" name="l00064"></a><span class="lineno"> 64</span><span class="comment">* 4: sin(eul[1])</span></div>
<div class="line"><a id="l00065" name="l00065"></a><span class="lineno"> 65</span><span class="comment">*</span></div>
<div class="line"><a id="l00066" name="l00066"></a><span class="lineno"> 66</span><span class="comment">* nphi,</span></div>
<div class="line"><a id="l00067" name="l00067"></a><span class="lineno"> 67</span><span class="comment">* ntheta int Vector lengths.</span></div>
<div class="line"><a id="l00068" name="l00068"></a><span class="lineno"> 68</span><span class="comment">*</span></div>
<div class="line"><a id="l00069" name="l00069"></a><span class="lineno"> 69</span><span class="comment">* spt,sxy int Vector strides.</span></div>
<div class="line"><a id="l00070" name="l00070"></a><span class="lineno"> 70</span><span class="comment">*</span></div>
<div class="line"><a id="l00071" name="l00071"></a><span class="lineno"> 71</span><span class="comment">* phi,theta const double[]</span></div>
<div class="line"><a id="l00072" name="l00072"></a><span class="lineno"> 72</span><span class="comment">* Longitude and latitude in the native coordinate</span></div>
<div class="line"><a id="l00073" name="l00073"></a><span class="lineno"> 73</span><span class="comment">* system of the projection [deg].</span></div>
<div class="line"><a id="l00074" name="l00074"></a><span class="lineno"> 74</span><span class="comment">*</span></div>
<div class="line"><a id="l00075" name="l00075"></a><span class="lineno"> 75</span><span class="comment">* Returned:</span></div>
<div class="line"><a id="l00076" name="l00076"></a><span class="lineno"> 76</span><span class="comment">* lng,lat double[] Celestial longitude and latitude [deg]. These may</span></div>
<div class="line"><a id="l00077" name="l00077"></a><span class="lineno"> 77</span><span class="comment">* refer to the same storage as phi and theta</span></div>
<div class="line"><a id="l00078" name="l00078"></a><span class="lineno"> 78</span><span class="comment">* respectively.</span></div>
<div class="line"><a id="l00079" name="l00079"></a><span class="lineno"> 79</span><span class="comment">*</span></div>
<div class="line"><a id="l00080" name="l00080"></a><span class="lineno"> 80</span><span class="comment">* Function return value:</span></div>
<div class="line"><a id="l00081" name="l00081"></a><span class="lineno"> 81</span><span class="comment">* int Status return value:</span></div>
<div class="line"><a id="l00082" name="l00082"></a><span class="lineno"> 82</span><span class="comment">* 0: Success.</span></div>
<div class="line"><a id="l00083" name="l00083"></a><span class="lineno"> 83</span><span class="comment">*</span></div>
<div class="line"><a id="l00084" name="l00084"></a><span class="lineno"> 84</span><span class="comment">*</span></div>
<div class="line"><a id="l00085" name="l00085"></a><span class="lineno"> 85</span><span class="comment">* sphs2x() - Rotation in the world-to-pixel direction</span></div>
<div class="line"><a id="l00086" name="l00086"></a><span class="lineno"> 86</span><span class="comment">* ---------------------------------------------------</span></div>
<div class="line"><a id="l00087" name="l00087"></a><span class="lineno"> 87</span><span class="comment">* sphs2x() transforms celestial coordinates to the native coordinates of a</span></div>
<div class="line"><a id="l00088" name="l00088"></a><span class="lineno"> 88</span><span class="comment">* projection.</span></div>
<div class="line"><a id="l00089" name="l00089"></a><span class="lineno"> 89</span><span class="comment">*</span></div>
<div class="line"><a id="l00090" name="l00090"></a><span class="lineno"> 90</span><span class="comment">* Given:</span></div>
<div class="line"><a id="l00091" name="l00091"></a><span class="lineno"> 91</span><span class="comment">* eul const double[5]</span></div>
<div class="line"><a id="l00092" name="l00092"></a><span class="lineno"> 92</span><span class="comment">* Euler angles for the transformation:</span></div>
<div class="line"><a id="l00093" name="l00093"></a><span class="lineno"> 93</span><span class="comment">* 0: Celestial longitude of the native pole [deg].</span></div>
<div class="line"><a id="l00094" name="l00094"></a><span class="lineno"> 94</span><span class="comment">* 1: Celestial colatitude of the native pole, or</span></div>
<div class="line"><a id="l00095" name="l00095"></a><span class="lineno"> 95</span><span class="comment">* native colatitude of the celestial pole [deg].</span></div>
<div class="line"><a id="l00096" name="l00096"></a><span class="lineno"> 96</span><span class="comment">* 2: Native longitude of the celestial pole [deg].</span></div>
<div class="line"><a id="l00097" name="l00097"></a><span class="lineno"> 97</span><span class="comment">* 3: cos(eul[1])</span></div>
<div class="line"><a id="l00098" name="l00098"></a><span class="lineno"> 98</span><span class="comment">* 4: sin(eul[1])</span></div>
<div class="line"><a id="l00099" name="l00099"></a><span class="lineno"> 99</span><span class="comment">*</span></div>
<div class="line"><a id="l00100" name="l00100"></a><span class="lineno"> 100</span><span class="comment">* nlng,nlat int Vector lengths.</span></div>
<div class="line"><a id="l00101" name="l00101"></a><span class="lineno"> 101</span><span class="comment">*</span></div>
<div class="line"><a id="l00102" name="l00102"></a><span class="lineno"> 102</span><span class="comment">* sll,spt int Vector strides.</span></div>
<div class="line"><a id="l00103" name="l00103"></a><span class="lineno"> 103</span><span class="comment">*</span></div>
<div class="line"><a id="l00104" name="l00104"></a><span class="lineno"> 104</span><span class="comment">* lng,lat const double[]</span></div>
<div class="line"><a id="l00105" name="l00105"></a><span class="lineno"> 105</span><span class="comment">* Celestial longitude and latitude [deg].</span></div>
<div class="line"><a id="l00106" name="l00106"></a><span class="lineno"> 106</span><span class="comment">*</span></div>
<div class="line"><a id="l00107" name="l00107"></a><span class="lineno"> 107</span><span class="comment">* Returned:</span></div>
<div class="line"><a id="l00108" name="l00108"></a><span class="lineno"> 108</span><span class="comment">* phi,theta double[] Longitude and latitude in the native coordinate system</span></div>
<div class="line"><a id="l00109" name="l00109"></a><span class="lineno"> 109</span><span class="comment">* of the projection [deg]. These may refer to the same</span></div>
<div class="line"><a id="l00110" name="l00110"></a><span class="lineno"> 110</span><span class="comment">* storage as lng and lat respectively.</span></div>
<div class="line"><a id="l00111" name="l00111"></a><span class="lineno"> 111</span><span class="comment">*</span></div>
<div class="line"><a id="l00112" name="l00112"></a><span class="lineno"> 112</span><span class="comment">* Function return value:</span></div>
<div class="line"><a id="l00113" name="l00113"></a><span class="lineno"> 113</span><span class="comment">* int Status return value:</span></div>
<div class="line"><a id="l00114" name="l00114"></a><span class="lineno"> 114</span><span class="comment">* 0: Success.</span></div>
<div class="line"><a id="l00115" name="l00115"></a><span class="lineno"> 115</span><span class="comment">*</span></div>
<div class="line"><a id="l00116" name="l00116"></a><span class="lineno"> 116</span><span class="comment">*</span></div>
<div class="line"><a id="l00117" name="l00117"></a><span class="lineno"> 117</span><span class="comment">* sphdpa() - Compute angular distance and position angle</span></div>
<div class="line"><a id="l00118" name="l00118"></a><span class="lineno"> 118</span><span class="comment">* ------------------------------------------------------</span></div>
<div class="line"><a id="l00119" name="l00119"></a><span class="lineno"> 119</span><span class="comment">* sphdpa() computes the angular distance and generalized position angle (see</span></div>
<div class="line"><a id="l00120" name="l00120"></a><span class="lineno"> 120</span><span class="comment">* notes) from a "reference" point to a number of "field" points on the sphere.</span></div>
<div class="line"><a id="l00121" name="l00121"></a><span class="lineno"> 121</span><span class="comment">* The points must be specified consistently in any spherical coordinate</span></div>
<div class="line"><a id="l00122" name="l00122"></a><span class="lineno"> 122</span><span class="comment">* system.</span></div>
<div class="line"><a id="l00123" name="l00123"></a><span class="lineno"> 123</span><span class="comment">*</span></div>
<div class="line"><a id="l00124" name="l00124"></a><span class="lineno"> 124</span><span class="comment">* sphdpa() is complementary to sphpad().</span></div>
<div class="line"><a id="l00125" name="l00125"></a><span class="lineno"> 125</span><span class="comment">*</span></div>
<div class="line"><a id="l00126" name="l00126"></a><span class="lineno"> 126</span><span class="comment">* Given:</span></div>
<div class="line"><a id="l00127" name="l00127"></a><span class="lineno"> 127</span><span class="comment">* nfield int The number of field points.</span></div>
<div class="line"><a id="l00128" name="l00128"></a><span class="lineno"> 128</span><span class="comment">*</span></div>
<div class="line"><a id="l00129" name="l00129"></a><span class="lineno"> 129</span><span class="comment">* lng0,lat0 double Spherical coordinates of the reference point [deg].</span></div>
<div class="line"><a id="l00130" name="l00130"></a><span class="lineno"> 130</span><span class="comment">*</span></div>
<div class="line"><a id="l00131" name="l00131"></a><span class="lineno"> 131</span><span class="comment">* lng,lat const double[]</span></div>
<div class="line"><a id="l00132" name="l00132"></a><span class="lineno"> 132</span><span class="comment">* Spherical coordinates of the field points [deg].</span></div>
<div class="line"><a id="l00133" name="l00133"></a><span class="lineno"> 133</span><span class="comment">*</span></div>
<div class="line"><a id="l00134" name="l00134"></a><span class="lineno"> 134</span><span class="comment">* Returned:</span></div>
<div class="line"><a id="l00135" name="l00135"></a><span class="lineno"> 135</span><span class="comment">* dist,pa double[] Angular distances and position angles [deg]. These</span></div>
<div class="line"><a id="l00136" name="l00136"></a><span class="lineno"> 136</span><span class="comment">* may refer to the same storage as lng and lat</span></div>
<div class="line"><a id="l00137" name="l00137"></a><span class="lineno"> 137</span><span class="comment">* respectively.</span></div>
<div class="line"><a id="l00138" name="l00138"></a><span class="lineno"> 138</span><span class="comment">*</span></div>
<div class="line"><a id="l00139" name="l00139"></a><span class="lineno"> 139</span><span class="comment">* Function return value:</span></div>
<div class="line"><a id="l00140" name="l00140"></a><span class="lineno"> 140</span><span class="comment">* int Status return value:</span></div>
<div class="line"><a id="l00141" name="l00141"></a><span class="lineno"> 141</span><span class="comment">* 0: Success.</span></div>
<div class="line"><a id="l00142" name="l00142"></a><span class="lineno"> 142</span><span class="comment">*</span></div>
<div class="line"><a id="l00143" name="l00143"></a><span class="lineno"> 143</span><span class="comment">* Notes:</span></div>
<div class="line"><a id="l00144" name="l00144"></a><span class="lineno"> 144</span><span class="comment">* 1. sphdpa() uses sphs2x() to rotate coordinates so that the reference</span></div>
<div class="line"><a id="l00145" name="l00145"></a><span class="lineno"> 145</span><span class="comment">* point is at the north pole of the new system with the north pole of the</span></div>
<div class="line"><a id="l00146" name="l00146"></a><span class="lineno"> 146</span><span class="comment">* old system at zero longitude in the new. The Euler angles required by</span></div>
<div class="line"><a id="l00147" name="l00147"></a><span class="lineno"> 147</span><span class="comment">* sphs2x() for this rotation are</span></div>
<div class="line"><a id="l00148" name="l00148"></a><span class="lineno"> 148</span><span class="comment">*</span></div>
<div class="line"><a id="l00149" name="l00149"></a><span class="lineno"> 149</span><span class="comment">= eul[0] = lng0;</span></div>
<div class="line"><a id="l00150" name="l00150"></a><span class="lineno"> 150</span><span class="comment">= eul[1] = 90.0 - lat0;</span></div>
<div class="line"><a id="l00151" name="l00151"></a><span class="lineno"> 151</span><span class="comment">= eul[2] = 0.0;</span></div>
<div class="line"><a id="l00152" name="l00152"></a><span class="lineno"> 152</span><span class="comment">*</span></div>
<div class="line"><a id="l00153" name="l00153"></a><span class="lineno"> 153</span><span class="comment">* The angular distance and generalized position angle are readily</span></div>
<div class="line"><a id="l00154" name="l00154"></a><span class="lineno"> 154</span><span class="comment">* obtained from the longitude and latitude of the field point in the new</span></div>
<div class="line"><a id="l00155" name="l00155"></a><span class="lineno"> 155</span><span class="comment">* system. This applies even if the reference point is at one of the</span></div>
<div class="line"><a id="l00156" name="l00156"></a><span class="lineno"> 156</span><span class="comment">* poles, in which case the "position angle" returned is as would be</span></div>
<div class="line"><a id="l00157" name="l00157"></a><span class="lineno"> 157</span><span class="comment">* computed for a reference point at (lng0,+90-epsilon) or</span></div>
<div class="line"><a id="l00158" name="l00158"></a><span class="lineno"> 158</span><span class="comment">* (lng0,-90+epsilon), in the limit as epsilon goes to zero.</span></div>
<div class="line"><a id="l00159" name="l00159"></a><span class="lineno"> 159</span><span class="comment">*</span></div>
<div class="line"><a id="l00160" name="l00160"></a><span class="lineno"> 160</span><span class="comment">* It is evident that the coordinate system in which the two points are</span></div>
<div class="line"><a id="l00161" name="l00161"></a><span class="lineno"> 161</span><span class="comment">* expressed is irrelevant to the determination of the angular separation</span></div>
<div class="line"><a id="l00162" name="l00162"></a><span class="lineno"> 162</span><span class="comment">* between the points. However, this is not true of the generalized</span></div>
<div class="line"><a id="l00163" name="l00163"></a><span class="lineno"> 163</span><span class="comment">* position angle.</span></div>
<div class="line"><a id="l00164" name="l00164"></a><span class="lineno"> 164</span><span class="comment">*</span></div>
<div class="line"><a id="l00165" name="l00165"></a><span class="lineno"> 165</span><span class="comment">* The generalized position angle is here defined as the angle of</span></div>
<div class="line"><a id="l00166" name="l00166"></a><span class="lineno"> 166</span><span class="comment">* intersection of the great circle containing the reference and field</span></div>
<div class="line"><a id="l00167" name="l00167"></a><span class="lineno"> 167</span><span class="comment">* points with that containing the reference point and the pole. It has</span></div>
<div class="line"><a id="l00168" name="l00168"></a><span class="lineno"> 168</span><span class="comment">* its normal meaning when the the reference and field points are</span></div>
<div class="line"><a id="l00169" name="l00169"></a><span class="lineno"> 169</span><span class="comment">* specified in equatorial coordinates (right ascension and declination).</span></div>
<div class="line"><a id="l00170" name="l00170"></a><span class="lineno"> 170</span><span class="comment">*</span></div>
<div class="line"><a id="l00171" name="l00171"></a><span class="lineno"> 171</span><span class="comment">* Interchanging the reference and field points changes the position angle</span></div>
<div class="line"><a id="l00172" name="l00172"></a><span class="lineno"> 172</span><span class="comment">* in a non-intuitive way (because the sum of the angles of a spherical</span></div>
<div class="line"><a id="l00173" name="l00173"></a><span class="lineno"> 173</span><span class="comment">* triangle normally exceeds 180 degrees).</span></div>
<div class="line"><a id="l00174" name="l00174"></a><span class="lineno"> 174</span><span class="comment">*</span></div>
<div class="line"><a id="l00175" name="l00175"></a><span class="lineno"> 175</span><span class="comment">* The position angle is undefined if the reference and field points are</span></div>
<div class="line"><a id="l00176" name="l00176"></a><span class="lineno"> 176</span><span class="comment">* coincident or antipodal. This may be detected by checking for a</span></div>
<div class="line"><a id="l00177" name="l00177"></a><span class="lineno"> 177</span><span class="comment">* distance of 0 or 180 degrees (within rounding tolerance). sphdpa()</span></div>
<div class="line"><a id="l00178" name="l00178"></a><span class="lineno"> 178</span><span class="comment">* will return an arbitrary position angle in such circumstances.</span></div>
<div class="line"><a id="l00179" name="l00179"></a><span class="lineno"> 179</span><span class="comment">*</span></div>
<div class="line"><a id="l00180" name="l00180"></a><span class="lineno"> 180</span><span class="comment">*</span></div>
<div class="line"><a id="l00181" name="l00181"></a><span class="lineno"> 181</span><span class="comment">* sphpad() - Compute field points offset from a given point</span></div>
<div class="line"><a id="l00182" name="l00182"></a><span class="lineno"> 182</span><span class="comment">* ---------------------------------------------------------</span></div>
<div class="line"><a id="l00183" name="l00183"></a><span class="lineno"> 183</span><span class="comment">* sphpad() computes the coordinates of a set of points that are offset by the</span></div>
<div class="line"><a id="l00184" name="l00184"></a><span class="lineno"> 184</span><span class="comment">* specified angular distances and position angles from a given "reference"</span></div>
<div class="line"><a id="l00185" name="l00185"></a><span class="lineno"> 185</span><span class="comment">* point on the sky. The distances and position angles must be specified</span></div>
<div class="line"><a id="l00186" name="l00186"></a><span class="lineno"> 186</span><span class="comment">* consistently in any spherical coordinate system.</span></div>
<div class="line"><a id="l00187" name="l00187"></a><span class="lineno"> 187</span><span class="comment">*</span></div>
<div class="line"><a id="l00188" name="l00188"></a><span class="lineno"> 188</span><span class="comment">* sphpad() is complementary to sphdpa().</span></div>
<div class="line"><a id="l00189" name="l00189"></a><span class="lineno"> 189</span><span class="comment">*</span></div>
<div class="line"><a id="l00190" name="l00190"></a><span class="lineno"> 190</span><span class="comment">* Given:</span></div>
<div class="line"><a id="l00191" name="l00191"></a><span class="lineno"> 191</span><span class="comment">* nfield int The number of field points.</span></div>
<div class="line"><a id="l00192" name="l00192"></a><span class="lineno"> 192</span><span class="comment">*</span></div>
<div class="line"><a id="l00193" name="l00193"></a><span class="lineno"> 193</span><span class="comment">* lng0,lat0 double Spherical coordinates of the reference point [deg].</span></div>
<div class="line"><a id="l00194" name="l00194"></a><span class="lineno"> 194</span><span class="comment">*</span></div>
<div class="line"><a id="l00195" name="l00195"></a><span class="lineno"> 195</span><span class="comment">* dist,pa const double[]</span></div>
<div class="line"><a id="l00196" name="l00196"></a><span class="lineno"> 196</span><span class="comment">* Angular distances and position angles [deg].</span></div>
<div class="line"><a id="l00197" name="l00197"></a><span class="lineno"> 197</span><span class="comment">*</span></div>
<div class="line"><a id="l00198" name="l00198"></a><span class="lineno"> 198</span><span class="comment">* Returned:</span></div>
<div class="line"><a id="l00199" name="l00199"></a><span class="lineno"> 199</span><span class="comment">* lng,lat double[] Spherical coordinates of the field points [deg].</span></div>
<div class="line"><a id="l00200" name="l00200"></a><span class="lineno"> 200</span><span class="comment">* These may refer to the same storage as dist and pa</span></div>
<div class="line"><a id="l00201" name="l00201"></a><span class="lineno"> 201</span><span class="comment">* respectively.</span></div>
<div class="line"><a id="l00202" name="l00202"></a><span class="lineno"> 202</span><span class="comment">*</span></div>
<div class="line"><a id="l00203" name="l00203"></a><span class="lineno"> 203</span><span class="comment">* Function return value:</span></div>
<div class="line"><a id="l00204" name="l00204"></a><span class="lineno"> 204</span><span class="comment">* int Status return value:</span></div>
<div class="line"><a id="l00205" name="l00205"></a><span class="lineno"> 205</span><span class="comment">* 0: Success.</span></div>
<div class="line"><a id="l00206" name="l00206"></a><span class="lineno"> 206</span><span class="comment">*</span></div>
<div class="line"><a id="l00207" name="l00207"></a><span class="lineno"> 207</span><span class="comment">* Notes:</span></div>
<div class="line"><a id="l00208" name="l00208"></a><span class="lineno"> 208</span><span class="comment">* 1: sphpad() is implemented analogously to sphdpa() although using sphx2s()</span></div>
<div class="line"><a id="l00209" name="l00209"></a><span class="lineno"> 209</span><span class="comment">* for the inverse transformation. In particular, when the reference</span></div>
<div class="line"><a id="l00210" name="l00210"></a><span class="lineno"> 210</span><span class="comment">* point is at one of the poles, "position angle" is interpreted as though</span></div>
<div class="line"><a id="l00211" name="l00211"></a><span class="lineno"> 211</span><span class="comment">* the reference point was at (lng0,+90-epsilon) or (lng0,-90+epsilon), in</span></div>
<div class="line"><a id="l00212" name="l00212"></a><span class="lineno"> 212</span><span class="comment">* the limit as epsilon goes to zero.</span></div>
<div class="line"><a id="l00213" name="l00213"></a><span class="lineno"> 213</span><span class="comment">*</span></div>
<div class="line"><a id="l00214" name="l00214"></a><span class="lineno"> 214</span><span class="comment">* Applying sphpad() with the distances and position angles computed by</span></div>
<div class="line"><a id="l00215" name="l00215"></a><span class="lineno"> 215</span><span class="comment">* sphdpa() should return the original field points.</span></div>
<div class="line"><a id="l00216" name="l00216"></a><span class="lineno"> 216</span><span class="comment">*</span></div>
<div class="line"><a id="l00217" name="l00217"></a><span class="lineno"> 217</span><span class="comment">*===========================================================================*/</span></div>
<div class="line"><a id="l00218" name="l00218"></a><span class="lineno"> 218</span> </div>
<div class="line"><a id="l00219" name="l00219"></a><span class="lineno"> 219</span><span class="preprocessor">#ifndef WCSLIB_SPH</span></div>
<div class="line"><a id="l00220" name="l00220"></a><span class="lineno"> 220</span><span class="preprocessor">#define WCSLIB_SPH</span></div>
<div class="line"><a id="l00221" name="l00221"></a><span class="lineno"> 221</span> </div>
<div class="line"><a id="l00222" name="l00222"></a><span class="lineno"> 222</span><span class="preprocessor">#ifdef __cplusplus</span></div>
<div class="line"><a id="l00223" name="l00223"></a><span class="lineno"> 223</span><span class="keyword">extern</span> <span class="stringliteral">"C"</span> {</div>
<div class="line"><a id="l00224" name="l00224"></a><span class="lineno"> 224</span><span class="preprocessor">#endif</span></div>
<div class="line"><a id="l00225" name="l00225"></a><span class="lineno"> 225</span> </div>
<div class="line"><a id="l00226" name="l00226"></a><span class="lineno"> 226</span> </div>
<div class="line"><a id="l00227" name="l00227"></a><span class="lineno"><a class="line" href="sph_8h.html#abcdbd119e57482315882d849f2b04e91"> 227</a></span><span class="keywordtype">int</span> <a class="code hl_function" href="sph_8h.html#abcdbd119e57482315882d849f2b04e91">sphx2s</a>(<span class="keyword">const</span> <span class="keywordtype">double</span> eul[5], <span class="keywordtype">int</span> nphi, <span class="keywordtype">int</span> ntheta, <span class="keywordtype">int</span> spt, <span class="keywordtype">int</span> sxy,</div>
<div class="line"><a id="l00228" name="l00228"></a><span class="lineno"> 228</span> <span class="keyword">const</span> <span class="keywordtype">double</span> phi[], <span class="keyword">const</span> <span class="keywordtype">double</span> theta[],</div>
<div class="line"><a id="l00229" name="l00229"></a><span class="lineno"> 229</span> <span class="keywordtype">double</span> lng[], <span class="keywordtype">double</span> lat[]);</div>
<div class="line"><a id="l00230" name="l00230"></a><span class="lineno"> 230</span> </div>
<div class="line"><a id="l00231" name="l00231"></a><span class="lineno"><a class="line" href="sph_8h.html#a5c0783d56189d48d9f52af05b64a4df6"> 231</a></span><span class="keywordtype">int</span> <a class="code hl_function" href="sph_8h.html#a5c0783d56189d48d9f52af05b64a4df6">sphs2x</a>(<span class="keyword">const</span> <span class="keywordtype">double</span> eul[5], <span class="keywordtype">int</span> nlng, <span class="keywordtype">int</span> nlat, <span class="keywordtype">int</span> sll , <span class="keywordtype">int</span> spt,</div>
<div class="line"><a id="l00232" name="l00232"></a><span class="lineno"> 232</span> <span class="keyword">const</span> <span class="keywordtype">double</span> lng[], <span class="keyword">const</span> <span class="keywordtype">double</span> lat[],</div>
<div class="line"><a id="l00233" name="l00233"></a><span class="lineno"> 233</span> <span class="keywordtype">double</span> phi[], <span class="keywordtype">double</span> theta[]);</div>
<div class="line"><a id="l00234" name="l00234"></a><span class="lineno"> 234</span> </div>
<div class="line"><a id="l00235" name="l00235"></a><span class="lineno"><a class="line" href="sph_8h.html#aec6222fe1e4d807c9b59980b8e548eb0"> 235</a></span><span class="keywordtype">int</span> <a class="code hl_function" href="sph_8h.html#aec6222fe1e4d807c9b59980b8e548eb0">sphdpa</a>(<span class="keywordtype">int</span> nfield, <span class="keywordtype">double</span> lng0, <span class="keywordtype">double</span> lat0,</div>
<div class="line"><a id="l00236" name="l00236"></a><span class="lineno"> 236</span> <span class="keyword">const</span> <span class="keywordtype">double</span> lng[], <span class="keyword">const</span> <span class="keywordtype">double</span> lat[],</div>
<div class="line"><a id="l00237" name="l00237"></a><span class="lineno"> 237</span> <span class="keywordtype">double</span> dist[], <span class="keywordtype">double</span> pa[]);</div>
<div class="line"><a id="l00238" name="l00238"></a><span class="lineno"> 238</span> </div>
<div class="line"><a id="l00239" name="l00239"></a><span class="lineno"><a class="line" href="sph_8h.html#a8ee2e117701f434f0bffbbe52f05d118"> 239</a></span><span class="keywordtype">int</span> <a class="code hl_function" href="sph_8h.html#a8ee2e117701f434f0bffbbe52f05d118">sphpad</a>(<span class="keywordtype">int</span> nfield, <span class="keywordtype">double</span> lng0, <span class="keywordtype">double</span> lat0,</div>
<div class="line"><a id="l00240" name="l00240"></a><span class="lineno"> 240</span> <span class="keyword">const</span> <span class="keywordtype">double</span> dist[], <span class="keyword">const</span> <span class="keywordtype">double</span> pa[],</div>
<div class="line"><a id="l00241" name="l00241"></a><span class="lineno"> 241</span> <span class="keywordtype">double</span> lng[], <span class="keywordtype">double</span> lat[]);</div>
<div class="line"><a id="l00242" name="l00242"></a><span class="lineno"> 242</span> </div>
<div class="line"><a id="l00243" name="l00243"></a><span class="lineno"> 243</span> </div>
<div class="line"><a id="l00244" name="l00244"></a><span class="lineno"> 244</span><span class="preprocessor">#ifdef __cplusplus</span></div>
<div class="line"><a id="l00245" name="l00245"></a><span class="lineno"> 245</span>}</div>
<div class="line"><a id="l00246" name="l00246"></a><span class="lineno"> 246</span><span class="preprocessor">#endif</span></div>
<div class="line"><a id="l00247" name="l00247"></a><span class="lineno"> 247</span> </div>
<div class="line"><a id="l00248" name="l00248"></a><span class="lineno"> 248</span><span class="preprocessor">#endif </span><span class="comment">// WCSLIB_SPH</span></div>
<div class="ttc" id="asph_8h_html_a5c0783d56189d48d9f52af05b64a4df6"><div class="ttname"><a href="sph_8h.html#a5c0783d56189d48d9f52af05b64a4df6">sphs2x</a></div><div class="ttdeci">int sphs2x(const double eul[5], int nlng, int nlat, int sll, int spt, const double lng[], const double lat[], double phi[], double theta[])</div><div class="ttdoc">Rotation in the world-to-pixel direction.</div></div>
<div class="ttc" id="asph_8h_html_a8ee2e117701f434f0bffbbe52f05d118"><div class="ttname"><a href="sph_8h.html#a8ee2e117701f434f0bffbbe52f05d118">sphpad</a></div><div class="ttdeci">int sphpad(int nfield, double lng0, double lat0, const double dist[], const double pa[], double lng[], double lat[])</div><div class="ttdoc">Compute field points offset from a given point.</div></div>
<div class="ttc" id="asph_8h_html_abcdbd119e57482315882d849f2b04e91"><div class="ttname"><a href="sph_8h.html#abcdbd119e57482315882d849f2b04e91">sphx2s</a></div><div class="ttdeci">int sphx2s(const double eul[5], int nphi, int ntheta, int spt, int sxy, const double phi[], const double theta[], double lng[], double lat[])</div><div class="ttdoc">Rotation in the pixel-to-world direction.</div></div>
<div class="ttc" id="asph_8h_html_aec6222fe1e4d807c9b59980b8e548eb0"><div class="ttname"><a href="sph_8h.html#aec6222fe1e4d807c9b59980b8e548eb0">sphdpa</a></div><div class="ttdeci">int sphdpa(int nfield, double lng0, double lat0, const double lng[], const double lat[], double dist[], double pa[])</div><div class="ttdoc">Compute angular distance and position angle.</div></div>
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