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| 74 | <a href="inrecgrid.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?format=raw" target="_TOP">view frames</a> summary: fields | routine details: <a href="#routine_details">routine</a> |
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| 81 | <h1 class="directory"><a href="directory-overview.html?format=raw">Interpolation/</a></h1> |
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| 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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| 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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| 91 | a point a given arc distance (-pi <= Arc_Dist <= pi), and azimuth (Az), |
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| 92 | from a specified location Lon0, lat0. |
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| 93 | Same as LL_ARC_DISTANCE but for n points without do loop. |
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[89] | 94 | |
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[101] | 95 | |
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| 96 | Formula from Map Projections - a working manual. USGS paper |
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| 97 | 1395. Equations (5-5) and (5-6). |
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| 98 | </div> |
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| 99 | |
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[89] | 100 | |
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| 107 | |
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| 108 | <div id="routine_details"> |
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| 109 | |
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| 110 | |
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| 111 | <div class="routine_details" id="_LL_NARCS_DISTANCES"> |
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| 112 | |
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[101] | 113 | <h2><a class="top" href="#container">top</a>LL_NARCS_DISTANCES <span class="categories"> Mapping, geography |
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| 114 | </span></h2> |
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[89] | 115 | |
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| 116 | <p class="header"> |
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| 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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| 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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[101] | 122 | <h3>Return value</h3><div class="value"> |
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| 123 | a (2, n) array containing the |
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[89] | 124 | longitude / latitude of the resultings points. Values are in radians |
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| 125 | unless the keyword DEGREES is set. |
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[101] | 126 | </div> |
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[89] | 127 | |
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| 128 | |
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| 129 | <h3>Parameters</h3> |
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| 130 | |
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| 131 | |
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| 132 | <h4 id="_LL_NARCS_DISTANCES_param_lon0">lon0 |
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[101] | 133 | <span class="attr">in</span> |
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[89] | 134 | |
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| 135 | |
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[101] | 136 | <span class="attr">required</span> |
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[89] | 137 | |
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| 138 | |
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| 139 | |
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| 140 | |
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| 141 | </h4> |
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| 142 | |
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[101] | 143 | <div class="comments"> An array containing the longitude of the starting point. |
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| 144 | Values are assumed to be in radians unless the keyword |
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| 145 | DEGREES is set.</div> |
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[89] | 146 | |
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| 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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[101] | 158 | <div class="comments"> An array containing the latitude of the starting point. |
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| 159 | Values are assumed to be in radians unless the keyword |
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| 160 | DEGREES is set.</div> |
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[89] | 161 | |
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| 162 | <h4 id="_LL_NARCS_DISTANCES_param_arc_dist">arc_dist |
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[101] | 163 | <span class="attr">in</span> |
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[89] | 164 | |
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| 165 | |
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[101] | 166 | <span class="attr">required</span> |
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[89] | 167 | |
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| 168 | |
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| 169 | |
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| 170 | |
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| 171 | </h4> |
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| 172 | |
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[101] | 173 | <div class="comments"> The arc distance from Lon_lat0. The value must be between |
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| 174 | -!PI and +!PI. To express distances in arc units, divide |
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| 175 | by the radius of the globe expressed in the original units. |
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| 176 | For example, if the radius of the earth is 6371 km, divide |
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| 177 | the distance in km by 6371 to obtain the arc distance. </div> |
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[89] | 178 | |
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| 179 | <h4 id="_LL_NARCS_DISTANCES_param_az">az |
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[101] | 180 | <span class="attr">in</span> |
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[89] | 181 | |
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| 182 | |
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[101] | 183 | <span class="attr">required</span> |
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[89] | 184 | |
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| 185 | |
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| 186 | |
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| 187 | |
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| 188 | </h4> |
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| 189 | |
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[101] | 190 | <div class="comments"> The azimuth from Lon_lat0. The value is assumed to be in |
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| 191 | radians unless the keyword DEGREES is set. |
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| 192 | </div> |
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[89] | 193 | |
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| 194 | |
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| 195 | |
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| 196 | |
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| 197 | |
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| 198 | |
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| 199 | <h3>Keywords</h3> |
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| 200 | |
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| 201 | <h4 id="_LL_NARCS_DISTANCES_keyword_DEGREES">DEGREES |
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| 202 | |
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| 203 | |
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| 204 | |
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| 205 | |
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| 206 | |
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| 208 | |
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| 209 | |
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| 210 | </h4> |
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| 211 | |
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[101] | 212 | <div class="comments"> Set this keyword to express all measurements and |
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| 213 | results in degrees. |
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| 214 | </div> |
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[89] | 215 | |
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| 216 | |
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| 217 | |
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[101] | 218 | <h3>Examples</h3><div class="value"> |
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| 219 | Result = LL_NARCS_DISTANCES(Lon, lat0, Arc_Dist, Az) |
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| 220 | |
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| 221 | |
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| 222 | Lon_lat0 = [1.0, 2.0]; Initial point specified in radians |
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| 223 | Arc_Dist = 2.0; Arc distance in radians |
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| 224 | Az = 1.0; Azimuth in radians |
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| 225 | Result = LL_ARC_DISTANCE(Lon_lat0, Arc_Dist, Az) |
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| 226 | PRINT, Result |
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| 227 | 2.91415 -0.622234 |
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| 228 | |
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| 229 | IDL> lon0 = [-10, 20, 100] |
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| 230 | IDL> lat0 = [0, -10, 45] |
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| 231 | IDL> lon1 = [10, 60, 280] |
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| 232 | IDL> lat1 = [0, 10, 45] |
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| 233 | IDL> dist = map_npoints(lon0, lat0, lon1, lat1, azimuth = azi, /two_by_two) |
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| 234 | IDL> earthradius = 6378206.4d0 |
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| 235 | IDL> res = ll_narcs_distances(lon0, lat0, dist/earthradius, azi, /degrees) |
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| 236 | IDL> print, reform(res[0, *]) |
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| 237 | 10.000000 60.000000 280.00000 |
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| 238 | IDL> print, reform(res[1, *]) |
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| 239 | 1.1999280e-15 10.000000 45.000000 |
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| 240 | </div> |
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| 241 | <h3>Version history</h3> |
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[89] | 242 | |
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| 243 | |
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[101] | 244 | <h4>History</h4><div class="value"> |
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| 245 | Based on the IDL function ll_arc_distance.pro,v 1.11 2003/02/03 |
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| 246 | Sebastien Masson (smasson@lodyc.jussieu.fr) |
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| 247 | August 2005</div> |
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| 266 | </div> |
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| 267 | |
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| 268 | </div> |
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| 272 | <div id="tagline">Produced by IDLdoc 2.0.</div> |
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