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74<a href="inrecgrid.html">&lt;&lt;prev file</a> | <a href="map_npoints.html">next file &gt;&gt;</a>&nbsp;&nbsp;&nbsp;&nbsp;<a href="ll_narcs_distances.html" target="_TOP">view single page</a> | <a href="./../index.html" target="_TOP">view frames</a>&nbsp;&nbsp;&nbsp;&nbsp;summary: fields | routine&nbsp;&nbsp;&nbsp;&nbsp;details: <a href="#routine_details">routine</a>
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81      <h1 class="directory"><a href="directory-overview.html">Interpolation/</a></h1>
82      <h2 class="pro_file">ll_narcs_distances.pro</h2>
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85        <dl>
86        </dl>
87      </div>
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89      <div id="file_comments">
90 This function returns the longitude and latitude [lon, lat] of
91 a point a given arc distance (-pi <= Arc_Dist <= pi), and azimuth (Az),
92 from a specified location Lon0, lat0.
93 Same as LL_ARC_DISTANCE but for n points without do loop.
94
95 Formula from Map Projections - a working manual.  USGS paper
96 1395. Equations (5-5) and (5-6).
97</div>
98
99     
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105     
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107      <div id="routine_details">
108       
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110        <div class="routine_details" id="_ll_narcs_distances">
111
112          <h2><a class="top" href="#container">top</a>ll_narcs_distances <span class="categories"> Mapping, geography
113</span></h2>
114       
115          <p class="header">
116            <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>
117       
118          <div class="comments">
119</div>
120
121          <h3>Return value</h3><div class="preformat">
122 a (2, n) array containing the longitude/latitude of the resulting points.
123 Values are in radians unless the keyword DEGREES is set.
124</div>
125
126         
127            <h3>Parameters</h3>
128       
129           
130            <h4 id="_ll_narcs_distances_param_lon0">lon0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
131              <span class="attr">in</span>
132             
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134              <span class="attr">required</span>
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138             
139            </h4>
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141          <div class="comments">
142 An array containing the longitude of the starting point.
143 Values are assumed to be in radians unless the keyword DEGREES is set.
144</div>
145           
146            <h4 id="_ll_narcs_distances_param_lat0">lat0&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
147              <span class="attr">in</span>
148             
149             
150              <span class="attr">required</span>
151             
152             
153             
154             
155            </h4>
156       
157          <div class="comments">
158 An array containing the latitude of the starting point.
159 Values are assumed to be in radians unless the keyword DEGREES is set.
160</div>
161           
162            <h4 id="_ll_narcs_distances_param_arc_dist">arc_dist&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
163              <span class="attr">in</span>
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166              <span class="attr">required</span>
167             
168             
169             
170             
171            </h4>
172       
173          <div class="comments">
174 The arc distance from Lon_lat0. The value must be between
175 -!PI and +!PI. To express distances in arc units, divide
176  by the radius of the globe expressed in the original units.
177  For example, if the radius of the earth is 6371 km, divide
178  the distance in km by 6371 to obtain the arc distance.
179</div>
180           
181            <h4 id="_ll_narcs_distances_param_az">az&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
182              <span class="attr">in</span>
183             
184             
185              <span class="attr">required</span>
186             
187             
188             
189             
190            </h4>
191       
192          <div class="comments">
193 The azimuth from Lon_lat0. The value is assumed to be in
194 radians unless the keyword DEGREES is set.
195</div>
196           
197
198         
199
200         
201
202            <h3>Keywords</h3>
203           
204            <h4 id="_ll_narcs_distances_keyword_DEGREES">DEGREES&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
205             
206             
207             
208             
209             
210             
211             
212             
213            </h4>
214       
215            <div class="comments">
216 Set this keyword to express all measurements and results in degrees.
217</div>
218           
219         
220
221          <h3>Examples</h3><div class="preformat">
222 IDL> Lon_lat0 = [1.0, 2.0]; Initial point specified in radians
223 IDL> Arc_Dist = 2.0; Arc distance in radians
224 IDL> Az = 1.0; Azimuth in radians
225 IDL> Result = LL_ARC_DISTANCE(Lon_lat0, Arc_Dist, Az)
226 IDL> PRINT, Result
227       2.91415    -0.622234
228
229 IDL> lon0 = [-10, 20, 100]
230 IDL> lat0 = [0, -10, 45]
231 IDL> lon1 = [10, 60, 280]
232 IDL> lat1 = [0, 10, 45]
233 IDL> dist = map_npoints(lon0, lat0, lon1, lat1, azimuth = azi, /two_by_two)
234 IDL> earthradius = 6378206.4d0
235 IDL> res = ll_narcs_distances(lon0, lat0, dist/earthradius, azi, /degrees)
236 IDL> print, reform(res[0, *])
237       10.000000       60.000000       280.00000
238 IDL> print, reform(res[1, *])
239           1.1999280e-15       10.000000       45.000000
240</div>
241          <h3>Version history</h3>
242         
243          <h4>Version</h4><div class="preformat"> $Id: ll_narcs_distances.pro 163 2006-08-29 12:59:46Z navarro $
244</div>
245          <h4>History</h4><div class="preformat">
246       Based on the IDL function ll_arc_distance.pro,v 1.11 2003/02/03
247 Sebastien Masson (smasson@lodyc.jussieu.fr)
248                  August 2005
249</div>
250         
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265       
266          <h3>Statistics</h3>
267          <table class="statistics">
268            <tr><td>McCabe cyclic</td><td>           5</td></tr>
269            <tr><td>McCabe essential</td><td>           1</td></tr>
270            <tr><td>McCabe modular design</td><td>           1</td></tr>
271          </table>
272         
273       
274        </div>
275       
276      </div>
277
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279
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