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| 5 | <title>ll_narcs_distances.pro (SAXO Documentation Assistant)</title> |
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| 47 | <td width="10%"> |
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[249] | 48 | <a href="lbcorca.html"><img src="./../prev.gif" border="0" alt="Previous"></a></td> |
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[163] | 49 | <td width="80%" align="center" valign="center"> |
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| 50 | <font size=-1><i>SAXO Documentation Assistant</i>: <a href="./../home.html">Overview</a></font></td> |
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| 51 | <td width="10%" align="right"> |
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| 52 | <a href="map_npoints.html"><img src="./../next.gif" border="0" alt="Next"></a></td> |
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| 53 | </tr> |
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| 54 | </table> |
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| 55 | |
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| 56 | |
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| 57 | <h1><font size="-2">Interpolation/</font></h1> |
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| 58 | <h2>ll_narcs_distances.pro</h2> |
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| 59 | |
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| 60 | <dl> |
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| 61 | </dl> |
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| 62 | |
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| 63 | |
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| 64 | This function returns the longitude and latitude [lon, lat] of |
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| 65 | a point a given arc distance (-pi <= Arc_Dist <= pi), and azimuth (Az), |
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[242] | 66 | from a specified location Lon0, Lat0. |
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[338] | 67 | 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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[163] | 68 | |
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| 69 | Formula from Map Projections - a working manual. USGS paper |
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| 70 | 1395. Equations (5-5) and (5-6). |
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| 71 | |
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| 72 | |
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| 73 | |
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| 74 | |
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| 75 | |
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| 76 | <a name="#_ll_narcs_distances"></a> |
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| 77 | |
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[242] | 78 | <h2>ll_narcs_distances <font size="-1" color="#006633"> |
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[234] | 79 | Mapping, geography |
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[163] | 80 | </font></h2> |
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| 81 | |
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| 82 | <p><font face="Courier"><i>result = </i>ll_narcs_distances(<i><a href="#_ll_narcs_distances_keyword_lon0">lon0</a>, <a href="#_ll_narcs_distances_keyword_lat0">lat0</a>, <a href="#_ll_narcs_distances_keyword_arc_dist">arc_dist</a>, <a href="#_ll_narcs_distances_keyword_az">az</a></i>, <a href="#_ll_narcs_distances_keyword_DEGREES">DEGREES</a>=<i>DEGREES</i>)</font></p> |
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| 83 | |
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| 84 | |
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| 85 | |
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| 86 | |
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| 87 | <h3>Return value</h3> |
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[242] | 88 | a (2,n) array containing the longitude/latitude of the resulting points. |
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[163] | 89 | Values are in radians unless the keyword DEGREES is set. |
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| 90 | |
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| 91 | |
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| 92 | |
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| 93 | <h3>Parameters</h3> |
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| 94 | |
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| 95 | |
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| 96 | <a name="#_ll_narcs_distances_keyword_lon0"></a> |
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| 97 | <h4>lon0 |
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| 98 | <font size="-1" color="#006633">in</font> |
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| 99 | |
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| 100 | |
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| 101 | <font size="-1" color="#006633">required</font> |
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| 102 | |
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| 103 | |
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| 104 | |
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| 105 | |
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| 106 | </h4> |
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| 107 | |
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| 108 | |
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| 109 | An array containing the longitude of the starting point. |
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| 110 | Values are assumed to be in radians unless the keyword DEGREES is set. |
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| 111 | |
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| 112 | |
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| 113 | |
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| 114 | <a name="#_ll_narcs_distances_keyword_lat0"></a> |
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| 115 | <h4>lat0 |
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| 116 | <font size="-1" color="#006633">in</font> |
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| 117 | |
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| 118 | |
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| 119 | <font size="-1" color="#006633">required</font> |
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| 120 | |
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| 121 | |
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| 122 | |
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| 123 | |
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| 124 | </h4> |
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| 125 | |
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| 126 | |
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| 127 | An array containing the latitude of the starting point. |
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| 128 | Values are assumed to be in radians unless the keyword DEGREES is set. |
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| 129 | |
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| 130 | |
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| 131 | |
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| 132 | <a name="#_ll_narcs_distances_keyword_arc_dist"></a> |
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| 133 | <h4>arc_dist |
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| 134 | <font size="-1" color="#006633">in</font> |
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| 135 | |
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| 136 | |
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| 137 | <font size="-1" color="#006633">required</font> |
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| 138 | |
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| 139 | |
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| 140 | |
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| 141 | |
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| 142 | </h4> |
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| 143 | |
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| 144 | |
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| 145 | The arc distance from Lon_lat0. The value must be between |
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| 146 | -!PI and +!PI. To express distances in arc units, divide |
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| 147 | by the radius of the globe expressed in the original units. |
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| 148 | For example, if the radius of the earth is 6371 km, divide |
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| 149 | the distance in km by 6371 to obtain the arc distance. |
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| 150 | |
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| 151 | |
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| 152 | |
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| 153 | <a name="#_ll_narcs_distances_keyword_az"></a> |
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| 154 | <h4>az |
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| 155 | <font size="-1" color="#006633">in</font> |
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| 156 | |
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| 157 | |
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| 158 | <font size="-1" color="#006633">required</font> |
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| 159 | |
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| 160 | |
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| 161 | |
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| 162 | |
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| 163 | </h4> |
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| 164 | |
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| 165 | |
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| 166 | The azimuth from Lon_lat0. The value is assumed to be in |
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| 167 | radians unless the keyword DEGREES is set. |
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| 168 | |
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| 169 | |
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| 170 | |
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| 171 | |
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| 172 | |
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| 173 | <h3>Keywords</h3> |
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| 174 | |
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| 175 | |
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| 176 | <a name="#_ll_narcs_distances_keyword_DEGREES"></a> |
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| 177 | <h4>DEGREES |
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| 178 | |
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| 179 | |
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| 180 | |
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| 181 | |
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| 182 | |
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| 183 | |
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| 184 | |
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| 185 | |
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| 186 | </h4> |
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| 187 | |
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| 188 | |
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| 189 | Set this keyword to express all measurements and results in degrees. |
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| 190 | |
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| 191 | |
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| 192 | |
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| 193 | |
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[234] | 194 | <h3>Examples</h3><pre> |
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[163] | 195 | IDL> Lon_lat0 = [1.0, 2.0]; Initial point specified in radians |
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| 196 | IDL> Arc_Dist = 2.0; Arc distance in radians |
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| 197 | IDL> Az = 1.0; Azimuth in radians |
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| 198 | IDL> Result = LL_ARC_DISTANCE(Lon_lat0, Arc_Dist, Az) |
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| 199 | IDL> PRINT, Result |
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| 200 | 2.91415 -0.622234 |
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| 201 | |
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| 202 | IDL> lon0 = [-10, 20, 100] |
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| 203 | IDL> lat0 = [0, -10, 45] |
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| 204 | IDL> lon1 = [10, 60, 280] |
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| 205 | IDL> lat1 = [0, 10, 45] |
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| 206 | IDL> dist = map_npoints(lon0, lat0, lon1, lat1, azimuth = azi, /two_by_two) |
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| 207 | IDL> earthradius = 6378206.4d0 |
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| 208 | IDL> res = ll_narcs_distances(lon0, lat0, dist/earthradius, azi, /degrees) |
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| 209 | IDL> print, reform(res[0, *]) |
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| 210 | 10.000000 60.000000 280.00000 |
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| 211 | IDL> print, reform(res[1, *]) |
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| 212 | 1.1999280e-15 10.000000 45.000000 |
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| 213 | |
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[234] | 214 | </pre><h3>Version history</h3> |
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[163] | 215 | |
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[234] | 216 | <h4>Version</h4> |
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[338] | 217 | $Id: ll_narcs_distances.pro 327 2007-12-13 16:22:35Z pinsard $ |
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[163] | 218 | |
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| 219 | <h4>History</h4> |
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| 220 | Based on the IDL function ll_arc_distance.pro,v 1.11 2003/02/03 |
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| 221 | Sebastien Masson (smasson@lodyc.jussieu.fr) |
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| 222 | August 2005 |
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| 240 | <font size="-3"><p> </p></font> |
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| 241 | <hr size="1" color="#CCCCCC"/> |
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[187] | 246 | <p><font color="gray" size="-3"> Produced by IDLdoc 2.0.</font></p> |
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[163] | 247 | |
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| 248 | </body> |
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[249] | 249 | </html> |
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