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[189] | 57 | <td><a href="../../../Interpolation//ll_narcs_distances.pro" title="Source code of a file">Source</a></td> |
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[249] | 74 | <a href="lbcorca.html"><<prev file</a> | <a href="map_npoints.html">next file >></a> <a href="ll_narcs_distances.html" target="_TOP">view single page</a> | <a href="./../index.html" target="_TOP">view frames</a> summary: fields | routine details: <a href="#routine_details">routine</a> |
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| 76 | </div> |
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[189] | 81 | <h1 class="directory"><a href="directory-overview.html">Interpolation/</a></h1> |
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[89] | 82 | <h2 class="pro_file">ll_narcs_distances.pro</h2> |
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| 83 | |
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| 84 | <div id="file_attr"> |
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| 86 | </dl> |
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| 87 | </div> |
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| 88 | |
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[101] | 89 | <div id="file_comments"> |
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| 90 | This function returns the longitude and latitude [lon, lat] of |
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[138] | 91 | a point a given arc distance (-pi <= Arc_Dist <= pi), and azimuth (Az), |
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[242] | 92 | from a specified location Lon0, Lat0. |
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[338] | 93 | Same as <a href="/Applications/itt/idl64/help/online_help/LL_ARC_DISTANCE.html">LL_ARC_DISTANCE</a> but for n points without do loop. |
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[89] | 94 | |
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[138] | 95 | Formula from Map Projections - a working manual. USGS paper |
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| 96 | 1395. Equations (5-5) and (5-6). |
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[101] | 97 | </div> |
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| 98 | |
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[89] | 99 | |
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| 101 | |
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| 106 | |
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| 107 | <div id="routine_details"> |
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| 108 | |
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| 109 | |
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[163] | 110 | <div class="routine_details" id="_ll_narcs_distances"> |
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[89] | 111 | |
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[242] | 112 | <h2><a class="top" href="#container">top</a>ll_narcs_distances <span class="categories"> |
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[234] | 113 | Mapping, geography |
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[101] | 114 | </span></h2> |
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[89] | 115 | |
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| 116 | <p class="header"> |
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[163] | 117 | <span class="result">result = </span>ll_narcs_distances(<span class="result"><a href="#_ll_narcs_distances_param_lon0">lon0</a>, <a href="#_ll_narcs_distances_param_lat0">lat0</a>, <a href="#_ll_narcs_distances_param_arc_dist">arc_dist</a>, <a href="#_ll_narcs_distances_param_az">az</a></span>, <a href="#_ll_narcs_distances_keyword_DEGREES">DEGREES</a>=<span class="result">DEGREES</span>)</p> |
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[89] | 118 | |
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| 119 | <div class="comments"> |
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[101] | 120 | </div> |
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[89] | 121 | |
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[138] | 122 | <h3>Return value</h3><div class="preformat"> |
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[242] | 123 | a (2,n) array containing the longitude/latitude of the resulting points. |
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[138] | 124 | Values are in radians unless the keyword DEGREES is set. |
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[101] | 125 | </div> |
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[89] | 126 | |
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| 127 | |
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| 128 | <h3>Parameters</h3> |
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| 129 | |
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| 130 | |
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[163] | 131 | <h4 id="_ll_narcs_distances_param_lon0">lon0 |
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[101] | 132 | <span class="attr">in</span> |
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[89] | 133 | |
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| 134 | |
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[101] | 135 | <span class="attr">required</span> |
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[89] | 136 | |
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| 137 | |
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| 138 | |
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| 139 | |
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| 140 | </h4> |
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| 141 | |
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[138] | 142 | <div class="comments"> |
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| 143 | An array containing the longitude of the starting point. |
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| 144 | Values are assumed to be in radians unless the keyword DEGREES is set. |
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| 145 | </div> |
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[89] | 146 | |
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[163] | 147 | <h4 id="_ll_narcs_distances_param_lat0">lat0 |
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[101] | 148 | <span class="attr">in</span> |
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[89] | 149 | |
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| 150 | |
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[101] | 151 | <span class="attr">required</span> |
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[89] | 152 | |
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| 153 | |
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| 154 | |
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| 155 | |
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| 156 | </h4> |
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| 157 | |
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[138] | 158 | <div class="comments"> |
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| 159 | An array containing the latitude of the starting point. |
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| 160 | Values are assumed to be in radians unless the keyword DEGREES is set. |
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| 161 | </div> |
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[89] | 162 | |
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[163] | 163 | <h4 id="_ll_narcs_distances_param_arc_dist">arc_dist |
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[101] | 164 | <span class="attr">in</span> |
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[89] | 165 | |
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| 166 | |
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[101] | 167 | <span class="attr">required</span> |
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[89] | 168 | |
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| 169 | |
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| 170 | |
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| 171 | |
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| 172 | </h4> |
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| 173 | |
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[138] | 174 | <div class="comments"> |
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| 175 | The arc distance from Lon_lat0. The value must be between |
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[101] | 176 | -!PI and +!PI. To express distances in arc units, divide |
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| 177 | by the radius of the globe expressed in the original units. |
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| 178 | For example, if the radius of the earth is 6371 km, divide |
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[138] | 179 | the distance in km by 6371 to obtain the arc distance. |
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| 180 | </div> |
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[89] | 181 | |
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[163] | 182 | <h4 id="_ll_narcs_distances_param_az">az |
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[101] | 183 | <span class="attr">in</span> |
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[89] | 184 | |
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| 185 | |
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[101] | 186 | <span class="attr">required</span> |
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[89] | 187 | |
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| 188 | |
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| 189 | |
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| 190 | |
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| 191 | </h4> |
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| 192 | |
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[138] | 193 | <div class="comments"> |
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| 194 | The azimuth from Lon_lat0. The value is assumed to be in |
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| 195 | radians unless the keyword DEGREES is set. |
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[101] | 196 | </div> |
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[89] | 197 | |
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| 198 | |
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| 199 | |
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| 202 | |
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| 203 | <h3>Keywords</h3> |
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| 204 | |
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[163] | 205 | <h4 id="_ll_narcs_distances_keyword_DEGREES">DEGREES |
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[89] | 206 | |
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| 213 | |
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| 214 | </h4> |
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| 215 | |
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[138] | 216 | <div class="comments"> |
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| 217 | Set this keyword to express all measurements and results in degrees. |
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[101] | 218 | </div> |
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[89] | 219 | |
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| 220 | |
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| 221 | |
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[138] | 222 | <h3>Examples</h3><div class="preformat"> |
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[121] | 223 | IDL> Lon_lat0 = [1.0, 2.0]; Initial point specified in radians |
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| 224 | IDL> Arc_Dist = 2.0; Arc distance in radians |
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| 225 | IDL> Az = 1.0; Azimuth in radians |
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| 226 | IDL> Result = LL_ARC_DISTANCE(Lon_lat0, Arc_Dist, Az) |
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| 227 | IDL> PRINT, Result |
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[101] | 228 | 2.91415 -0.622234 |
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| 229 | |
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[138] | 230 | IDL> lon0 = [-10, 20, 100] |
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| 231 | IDL> lat0 = [0, -10, 45] |
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| 232 | IDL> lon1 = [10, 60, 280] |
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| 233 | IDL> lat1 = [0, 10, 45] |
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| 234 | IDL> dist = map_npoints(lon0, lat0, lon1, lat1, azimuth = azi, /two_by_two) |
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| 235 | IDL> earthradius = 6378206.4d0 |
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| 236 | IDL> res = ll_narcs_distances(lon0, lat0, dist/earthradius, azi, /degrees) |
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| 237 | IDL> print, reform(res[0, *]) |
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[101] | 238 | 10.000000 60.000000 280.00000 |
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[138] | 239 | IDL> print, reform(res[1, *]) |
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| 240 | 1.1999280e-15 10.000000 45.000000 |
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[101] | 241 | </div> |
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| 242 | <h3>Version history</h3> |
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[89] | 243 | |
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[234] | 244 | <h4>Version</h4><div class="preformat"> |
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[338] | 245 | $Id: ll_narcs_distances.pro 327 2007-12-13 16:22:35Z pinsard $ |
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[118] | 246 | </div> |
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[138] | 247 | <h4>History</h4><div class="preformat"> |
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[101] | 248 | Based on the IDL function ll_arc_distance.pro,v 1.11 2003/02/03 |
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| 249 | Sebastien Masson (smasson@lodyc.jussieu.fr) |
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[118] | 250 | August 2005 |
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| 251 | </div> |
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[89] | 252 | |
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[163] | 268 | <h3>Statistics</h3> |
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| 269 | <table class="statistics"> |
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| 270 | <tr><td>McCabe cyclic</td><td> 5</td></tr> |
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| 271 | <tr><td>McCabe essential</td><td> 1</td></tr> |
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| 272 | <tr><td>McCabe modular design</td><td> 1</td></tr> |
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| 273 | </table> |
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[89] | 274 | |
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| 276 | </div> |
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| 277 | |
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| 282 | <div id="tagline">Produced by IDLdoc 2.0.</div> |
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