libs/geometry/doc/html/geometry/reference/algorithms/area/area_2_with_strategy.html

   1 <html>
   2 <head>
   3 <meta http-equiv="Content-Type" content="text/html; charset=US-ASCII">
   4 <title>area (with strategy)</title>
   5 <link rel="stylesheet" href="../../../../../../../../doc/src/boostbook.css" type="text/css">
   6 <meta name="generator" content="DocBook XSL Stylesheets V1.79.1">
   7 <link rel="home" href="../../../../index.html" title="Chapter&#160;1.&#160;Geometry">
   8 <link rel="up" href="../area.html" title="area">
   9 <link rel="prev" href="area_1.html" title="area">
  10 <link rel="next" href="../assign.html" title="assign">
  11 </head>
  12 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
  13 <table cellpadding="2" width="100%"><tr>
  14 <td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../../boost.png"></td>
  15 <td align="center"><a href="../../../../../../../../index.html">Home</a></td>
  16 <td align="center"><a href="../../../../../../../../libs/libraries.htm">Libraries</a></td>
  17 <td align="center"><a href="http://www.boost.org/users/people.html">People</a></td>
  18 <td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td>
  19 <td align="center"><a href="../../../../../../../../more/index.htm">More</a></td>
  20 </tr></table>
  21 <hr>
  22 <div class="spirit-nav">
  23 <a accesskey="p" href="area_1.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../area.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../assign.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a>
  24 </div>
  25 <div class="section">
  26 <div class="titlepage"><div><div><h5 class="title">
  27 <a name="geometry.reference.algorithms.area.area_2_with_strategy"></a><a class="link" href="area_2_with_strategy.html" title="area (with strategy)">area
  28           (with strategy)</a>
  29 </h5></div></div></div>
  30 <p>
  31             <a class="indexterm" name="idp87958352"></a>
  32 Calculates the area of a geometry using the specified strategy.
  33           </p>
  34 <h6>
  35 <a name="geometry.reference.algorithms.area.area_2_with_strategy.h0"></a>
  36             <span class="phrase"><a name="geometry.reference.algorithms.area.area_2_with_strategy.description"></a></span><a class="link" href="area_2_with_strategy.html#geometry.reference.algorithms.area.area_2_with_strategy.description">Description</a>
  37           </h6>
  38 <p>
  39             The free function area calculates the area of a geometry using the specified
  40             strategy. Reasons to specify a strategy include: use another coordinate
  41             system for calculations; construct the strategy beforehand (e.g. with
  42             the radius of the Earth); select a strategy when there are more than
  43             one available for a calculation.
  44           </p>
  45 <h6>
  46 <a name="geometry.reference.algorithms.area.area_2_with_strategy.h1"></a>
  47             <span class="phrase"><a name="geometry.reference.algorithms.area.area_2_with_strategy.synopsis"></a></span><a class="link" href="area_2_with_strategy.html#geometry.reference.algorithms.area.area_2_with_strategy.synopsis">Synopsis</a>
  48           </h6>
  49 <p>
  50 </p>
  51 <pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span><span class="keyword">typename</span> <span class="identifier">Geometry</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Strategy</span><span class="special">&gt;</span>
  52 <span class="identifier">Strategy</span><span class="special">::</span><span class="identifier">return_type</span> <span class="identifier">area</span><span class="special">(</span><span class="identifier">Geometry</span> <span class="keyword">const</span> <span class="special">&amp;</span> <span class="identifier">geometry</span><span class="special">,</span> <span class="identifier">Strategy</span> <span class="keyword">const</span> <span class="special">&amp;</span> <span class="identifier">strategy</span><span class="special">)</span></pre>
  53 <p>
  54           </p>
  55 <h6>
  56 <a name="geometry.reference.algorithms.area.area_2_with_strategy.h2"></a>
  57             <span class="phrase"><a name="geometry.reference.algorithms.area.area_2_with_strategy.parameters"></a></span><a class="link" href="area_2_with_strategy.html#geometry.reference.algorithms.area.area_2_with_strategy.parameters">Parameters</a>
  58           </h6>
  59 <div class="informaltable"><table class="table">
  60 <colgroup>
  61 <col>
  62 <col>
  63 <col>
  64 <col>
  65 </colgroup>
  66 <thead><tr>
  67 <th>
  68                     <p>
  69                       Type
  70                     </p>
  71                   </th>
  72 <th>
  73                     <p>
  74                       Concept
  75                     </p>
  76                   </th>
  77 <th>
  78                     <p>
  79                       Name
  80                     </p>
  81                   </th>
  82 <th>
  83                     <p>
  84                       Description
  85                     </p>
  86                   </th>
  87 </tr></thead>
  88 <tbody>
  89 <tr>
  90 <td>
  91                     <p>
  92                       Geometry const &amp;
  93                     </p>
  94                   </td>
  95 <td>
  96                     <p>
  97                       Any type fulfilling a Geometry Concept
  98                     </p>
  99                   </td>
 100 <td>
 101                     <p>
 102                       geometry
 103                     </p>
 104                   </td>
 105 <td>
 106                     <p>
 107                       A model of the specified concept
 108                     </p>
 109                   </td>
 110 </tr>
 111 <tr>
 112 <td>
 113                     <p>
 114                       Strategy const &amp;
 115                     </p>
 116                   </td>
 117 <td>
 118                     <p>
 119                       Any type fulfilling a Area Strategy Concept
 120                     </p>
 121                   </td>
 122 <td>
 123                     <p>
 124                       strategy
 125                     </p>
 126                   </td>
 127 <td>
 128                     <p>
 129                       The strategy which will be used for area calculations
 130                     </p>
 131                   </td>
 132 </tr>
 133 </tbody>
 134 </table></div>
 135 <h6>
 136 <a name="geometry.reference.algorithms.area.area_2_with_strategy.h3"></a>
 137             <span class="phrase"><a name="geometry.reference.algorithms.area.area_2_with_strategy.returns"></a></span><a class="link" href="area_2_with_strategy.html#geometry.reference.algorithms.area.area_2_with_strategy.returns">Returns</a>
 138           </h6>
 139 <p>
 140             The calculated area
 141           </p>
 142 <h6>
 143 <a name="geometry.reference.algorithms.area.area_2_with_strategy.h4"></a>
 144             <span class="phrase"><a name="geometry.reference.algorithms.area.area_2_with_strategy.header"></a></span><a class="link" href="area_2_with_strategy.html#geometry.reference.algorithms.area.area_2_with_strategy.header">Header</a>
 145           </h6>
 146 <p>
 147             Either
 148           </p>
 149 <p>
 150             <code class="computeroutput"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
 151           </p>
 152 <p>
 153             Or
 154           </p>
 155 <p>
 156             <code class="computeroutput"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">algorithms</span><span class="special">/</span><span class="identifier">area</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span></code>
 157           </p>
 158 <h6>
 159 <a name="geometry.reference.algorithms.area.area_2_with_strategy.h5"></a>
 160             <span class="phrase"><a name="geometry.reference.algorithms.area.area_2_with_strategy.conformance"></a></span><a class="link" href="area_2_with_strategy.html#geometry.reference.algorithms.area.area_2_with_strategy.conformance">Conformance</a>
 161           </h6>
 162 <p>
 163             The function area implements function Area from the <a href="http://www.opengeospatial.org/standards/sfa" target="_top">OGC
 164             Simple Feature Specification</a>.
 165           </p>
 166 <h6>
 167 <a name="geometry.reference.algorithms.area.area_2_with_strategy.h6"></a>
 168             <span class="phrase"><a name="geometry.reference.algorithms.area.area_2_with_strategy.behavior"></a></span><a class="link" href="area_2_with_strategy.html#geometry.reference.algorithms.area.area_2_with_strategy.behavior">Behavior</a>
 169           </h6>
 170 <div class="informaltable"><table class="table">
 171 <colgroup>
 172 <col>
 173 <col>
 174 </colgroup>
 175 <thead><tr>
 176 <th>
 177                     <p>
 178                       Case
 179                     </p>
 180                   </th>
 181 <th>
 182                     <p>
 183                       Behavior
 184                     </p>
 185                   </th>
 186 </tr></thead>
 187 <tbody>
 188 <tr>
 189 <td>
 190                     <p>
 191                       pointlike (e.g. point)
 192                     </p>
 193                   </td>
 194 <td>
 195                     <p>
 196                       Returns 0
 197                     </p>
 198                   </td>
 199 </tr>
 200 <tr>
 201 <td>
 202                     <p>
 203                       linear (e.g. linestring)
 204                     </p>
 205                   </td>
 206 <td>
 207                     <p>
 208                       Returns 0
 209                     </p>
 210                   </td>
 211 </tr>
 212 <tr>
 213 <td>
 214                     <p>
 215                       areal (e.g. polygon)
 216                     </p>
 217                   </td>
 218 <td>
 219                     <p>
 220                       Returns the area
 221                     </p>
 222                   </td>
 223 </tr>
 224 <tr>
 225 <td>
 226                     <p>
 227                       Cartesian
 228                     </p>
 229                   </td>
 230 <td>
 231                     <p>
 232                       Returns the area in the same units as the input coordinates
 233                     </p>
 234                   </td>
 235 </tr>
 236 <tr>
 237 <td>
 238                     <p>
 239                       Spherical
 240                     </p>
 241                   </td>
 242 <td>
 243                     <p>
 244                       Returns the area on a unit sphere (or another sphere, if specified
 245                       as such in the constructor of the strategy)
 246                     </p>
 247                   </td>
 248 </tr>
 249 <tr>
 250 <td>
 251                     <p>
 252                       Reversed polygon (coordinates not according their orientiation)
 253                     </p>
 254                   </td>
 255 <td>
 256                     <p>
 257                       Returns the negative area
 258                     </p>
 259                   </td>
 260 </tr>
 261 </tbody>
 262 </table></div>
 263 <h6>
 264 <a name="geometry.reference.algorithms.area.area_2_with_strategy.h7"></a>
 265             <span class="phrase"><a name="geometry.reference.algorithms.area.area_2_with_strategy.supported_geometries"></a></span><a class="link" href="area_2_with_strategy.html#geometry.reference.algorithms.area.area_2_with_strategy.supported_geometries">Supported
 266             geometries</a>
 267           </h6>
 268 <div class="informaltable"><table class="table">
 269 <colgroup>
 270 <col>
 271 <col>
 272 </colgroup>
 273 <thead><tr>
 274 <th>
 275                     <p>
 276                       Geometry
 277                     </p>
 278                   </th>
 279 <th>
 280                     <p>
 281                       Status
 282                     </p>
 283                   </th>
 284 </tr></thead>
 285 <tbody>
 286 <tr>
 287 <td>
 288                     <p>
 289                       Point
 290                     </p>
 291                   </td>
 292 <td>
 293                     <p>
 294                       <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span>
 295                     </p>
 296                   </td>
 297 </tr>
 298 <tr>
 299 <td>
 300                     <p>
 301                       Segment
 302                     </p>
 303                   </td>
 304 <td>
 305                     <p>
 306                       <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span>
 307                     </p>
 308                   </td>
 309 </tr>
 310 <tr>
 311 <td>
 312                     <p>
 313                       Box
 314                     </p>
 315                   </td>
 316 <td>
 317                     <p>
 318                       <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span>
 319                     </p>
 320                   </td>
 321 </tr>
 322 <tr>
 323 <td>
 324                     <p>
 325                       Linestring
 326                     </p>
 327                   </td>
 328 <td>
 329                     <p>
 330                       <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span>
 331                     </p>
 332                   </td>
 333 </tr>
 334 <tr>
 335 <td>
 336                     <p>
 337                       Ring
 338                     </p>
 339                   </td>
 340 <td>
 341                     <p>
 342                       <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span>
 343                     </p>
 344                   </td>
 345 </tr>
 346 <tr>
 347 <td>
 348                     <p>
 349                       Polygon
 350                     </p>
 351                   </td>
 352 <td>
 353                     <p>
 354                       <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span>
 355                     </p>
 356                   </td>
 357 </tr>
 358 <tr>
 359 <td>
 360                     <p>
 361                       MultiPoint
 362                     </p>
 363                   </td>
 364 <td>
 365                     <p>
 366                       <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span>
 367                     </p>
 368                   </td>
 369 </tr>
 370 <tr>
 371 <td>
 372                     <p>
 373                       MultiLinestring
 374                     </p>
 375                   </td>
 376 <td>
 377                     <p>
 378                       <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span>
 379                     </p>
 380                   </td>
 381 </tr>
 382 <tr>
 383 <td>
 384                     <p>
 385                       MultiPolygon
 386                     </p>
 387                   </td>
 388 <td>
 389                     <p>
 390                       <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span>
 391                     </p>
 392                   </td>
 393 </tr>
 394 <tr>
 395 <td>
 396                     <p>
 397                       Variant
 398                     </p>
 399                   </td>
 400 <td>
 401                     <p>
 402                       <span class="inlinemediaobject"><img src="../../../../img/ok.png" alt="ok"></span>
 403                     </p>
 404                   </td>
 405 </tr>
 406 </tbody>
 407 </table></div>
 408 <h6>
 409 <a name="geometry.reference.algorithms.area.area_2_with_strategy.h8"></a>
 410             <span class="phrase"><a name="geometry.reference.algorithms.area.area_2_with_strategy.complexity"></a></span><a class="link" href="area_2_with_strategy.html#geometry.reference.algorithms.area.area_2_with_strategy.complexity">Complexity</a>
 411           </h6>
 412 <p>
 413             Linear
 414           </p>
 415 <h6>
 416 <a name="geometry.reference.algorithms.area.area_2_with_strategy.h9"></a>
 417             <span class="phrase"><a name="geometry.reference.algorithms.area.area_2_with_strategy.example"></a></span><a class="link" href="area_2_with_strategy.html#geometry.reference.algorithms.area.area_2_with_strategy.example">Example</a>
 418           </h6>
 419 <p>
 420             Calculate the area of a polygon
 421           </p>
 422 <p>
 423 </p>
 424 <pre class="programlisting"><span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">iostream</span><span class="special">&gt;</span>
 425
 426 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 427 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">geometries</span><span class="special">/</span><span class="identifier">point_xy</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 428 <span class="preprocessor">#include</span> <span class="special">&lt;</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">geometries</span><span class="special">/</span><span class="identifier">polygon</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">&gt;</span>
 429
 430 <span class="keyword">namespace</span> <span class="identifier">bg</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">;</span> <a class="co" name="geometry.reference.algorithms.area.area_2_with_strategy.c0" href="area_2_with_strategy.html#geometry.reference.algorithms.area.area_2_with_strategy.c1"><img src="../../../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a>
 431
 432 <span class="keyword">int</span> <span class="identifier">main</span><span class="special">()</span>
 433 <span class="special">{</span>
 434     <span class="comment">// Calculate the area of a cartesian polygon</span>
 435     <span class="identifier">bg</span><span class="special">::</span><span class="identifier">model</span><span class="special">::</span><span class="identifier">polygon</span><span class="special">&lt;</span><span class="identifier">bg</span><span class="special">::</span><span class="identifier">model</span><span class="special">::</span><span class="identifier">d2</span><span class="special">::</span><span class="identifier">point_xy</span><span class="special">&lt;</span><span class="keyword">double</span><span class="special">&gt;</span> <span class="special">&gt;</span> <span class="identifier">poly</span><span class="special">;</span>
 436     <span class="identifier">bg</span><span class="special">::</span><span class="identifier">read_wkt</span><span class="special">(</span><span class="string">"POLYGON((0 0,0 7,4 2,2 0,0 0))"</span><span class="special">,</span> <span class="identifier">poly</span><span class="special">);</span>
 437     <span class="keyword">double</span> <span class="identifier">area</span> <span class="special">=</span> <span class="identifier">bg</span><span class="special">::</span><span class="identifier">area</span><span class="special">(</span><span class="identifier">poly</span><span class="special">);</span>
 438     <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"Area: "</span> <span class="special">&lt;&lt;</span> <span class="identifier">area</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
 439
 440     <span class="comment">// Calculate the area of a spherical polygon (for latitude: 0 at equator)</span>
 441     <span class="identifier">bg</span><span class="special">::</span><span class="identifier">model</span><span class="special">::</span><span class="identifier">polygon</span><span class="special">&lt;</span><span class="identifier">bg</span><span class="special">::</span><span class="identifier">model</span><span class="special">::</span><span class="identifier">point</span><span class="special">&lt;</span><span class="keyword">float</span><span class="special">,</span> <span class="number">2</span><span class="special">,</span> <span class="identifier">bg</span><span class="special">::</span><span class="identifier">cs</span><span class="special">::</span><span class="identifier">spherical_equatorial</span><span class="special">&lt;</span><span class="identifier">bg</span><span class="special">::</span><span class="identifier">degree</span><span class="special">&gt;</span> <span class="special">&gt;</span> <span class="special">&gt;</span> <span class="identifier">sph_poly</span><span class="special">;</span>
 442     <span class="identifier">bg</span><span class="special">::</span><span class="identifier">read_wkt</span><span class="special">(</span><span class="string">"POLYGON((0 0,0 45,45 0,0 0))"</span><span class="special">,</span> <span class="identifier">sph_poly</span><span class="special">);</span>
 443     <span class="identifier">area</span> <span class="special">=</span> <span class="identifier">bg</span><span class="special">::</span><span class="identifier">area</span><span class="special">(</span><span class="identifier">sph_poly</span><span class="special">);</span>
 444     <span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special">&lt;&lt;</span> <span class="string">"Area: "</span> <span class="special">&lt;&lt;</span> <span class="identifier">area</span> <span class="special">&lt;&lt;</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
 445
 446     <span class="keyword">return</span> <span class="number">0</span><span class="special">;</span>
 447 <span class="special">}</span>
 448 </pre>
 449 <p>
 450           </p>
 451 <div class="calloutlist"><table border="0" summary="Callout list"><tr>
 452 <td width="5%" valign="top" align="left"><p><a name="geometry.reference.algorithms.area.area_2_with_strategy.c1"></a><a href="#geometry.reference.algorithms.area.area_2_with_strategy.c0"><img src="../../../../../../../../doc/src/images/callouts/1.png" alt="1" border="0"></a> </p></td>
 453 <td valign="top" align="left"><p>
 454                 Convenient namespace alias
 455               </p></td>
 456 </tr></table></div>
 457 <p>
 458             Output:
 459           </p>
 460 <pre class="programlisting">Area: 16
 461 Area: 0.339837
 462 </pre>
 463 <h6>
 464 <a name="geometry.reference.algorithms.area.area_2_with_strategy.h10"></a>
 465             <span class="phrase"><a name="geometry.reference.algorithms.area.area_2_with_strategy.available_strategies"></a></span><a class="link" href="area_2_with_strategy.html#geometry.reference.algorithms.area.area_2_with_strategy.available_strategies">Available
 466             Strategies</a>
 467           </h6>
 468 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
 469 <li class="listitem">
 470                 <a class="link" href="../../strategies/strategy_area_surveyor.html" title="strategy::area::surveyor">Surveyor
 471                 (cartesian)</a>
 472               </li>
 473 <li class="listitem">
 474                 <a class="link" href="../../strategies/strategy_area_spherical.html" title="strategy::area::spherical">Spherical</a>
 475               </li>
 476 </ul></div>
 477 </div>
 478 <table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr>
 479 <td align="left"></td>
 480 <td align="right"><div class="copyright-footer">Copyright &#169; 2009-2017 Barend
 481       Gehrels, Bruno Lalande, Mateusz Loskot, Adam Wulkiewicz, Oracle and/or its
 482       affiliates<p>
 483         Distributed under the Boost Software License, Version 1.0. (See accompanying
 484         file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
 485       </p>
 486 </div></td>
 487 </tr></table>
 488 <hr>
 489 <div class="spirit-nav">
 490 <a accesskey="p" href="area_1.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../area.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../assign.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a>
 491 </div>
 492 </body>
 493 </html>