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<div class="titlepage"><div><div><h3 class="title">
<a name="geometry.spatial_indexes.rtree_quickstart"></a><a class="link" href="rtree_quickstart.html" title="Quick Start">Quick Start</a>
</h3></div></div></div>
<p>
This Quick Start section shows simple way to creating a typical R-tree and
perform spatial query.
</p>
<p>
The code below assumes that following files are included and namespaces used.
</p>
<p>
</p>
<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</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">></span>
<span class="preprocessor">#include</span> <span class="special"><</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</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
<span class="preprocessor">#include</span> <span class="special"><</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">box</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">geometry</span><span class="special">/</span><span class="identifier">index</span><span class="special">/</span><span class="identifier">rtree</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
<span class="comment">// to store queries results</span>
<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">vector</span><span class="special">></span>
<span class="comment">// just for output</span>
<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">iostream</span><span class="special">></span>
<span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">foreach</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span>
<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>
<span class="keyword">namespace</span> <span class="identifier">bgi</span> <span class="special">=</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">index</span><span class="special">;</span>
</pre>
<p>
</p>
<p>
Typically you'll store e.g. <code class="computeroutput"><span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">Box</span><span class="special">,</span> <span class="identifier">MyGeometryId</span><span class="special">></span></code> in the R-tree. <code class="computeroutput"><span class="identifier">MyGeometryId</span></code>
will be some identifier of a complex <code class="computeroutput"><span class="identifier">Geometry</span></code>
stored in other container, e.g. index type of a <code class="computeroutput"><span class="identifier">Polygon</span></code>
stored in the vector or an iterator of list of <code class="computeroutput"><span class="identifier">Ring</span></code>s.
To keep it simple to define <code class="computeroutput"><span class="identifier">Value</span></code>
we will use predefined Box and unsigned int.
</p>
<p>
</p>
<pre class="programlisting"><span class="keyword">typedef</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"><</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">cartesian</span><span class="special">></span> <span class="identifier">point</span><span class="special">;</span>
<span class="keyword">typedef</span> <span class="identifier">bg</span><span class="special">::</span><span class="identifier">model</span><span class="special">::</span><span class="identifier">box</span><span class="special"><</span><span class="identifier">point</span><span class="special">></span> <span class="identifier">box</span><span class="special">;</span>
<span class="keyword">typedef</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">pair</span><span class="special"><</span><span class="identifier">box</span><span class="special">,</span> <span class="keyword">unsigned</span><span class="special">></span> <span class="identifier">value</span><span class="special">;</span>
</pre>
<p>
</p>
<p>
R-tree may be created using various algorithm and parameters. You should
choose the algorithm you'll find the best for your purpose. In this example
we will use quadratic algorithm. Parameters are passed as template parameters.
Maximum number of elements in nodes is set to 16.
</p>
<p>
</p>
<pre class="programlisting"><span class="comment">// create the rtree using default constructor</span>
<span class="identifier">bgi</span><span class="special">::</span><span class="identifier">rtree</span><span class="special"><</span> <span class="identifier">value</span><span class="special">,</span> <span class="identifier">bgi</span><span class="special">::</span><span class="identifier">quadratic</span><span class="special"><</span><span class="number">16</span><span class="special">></span> <span class="special">></span> <span class="identifier">rtree</span><span class="special">;</span>
</pre>
<p>
</p>
<p>
Typically <code class="computeroutput"><span class="identifier">Value</span></code>s will be
generated in a loop from e.g. <code class="computeroutput"><span class="identifier">Polygon</span></code>s
stored in some other container. In this case <code class="computeroutput"><span class="identifier">Box</span></code>
objects will probably be created with <code class="computeroutput"><span class="identifier">geometry</span><span class="special">::</span><span class="identifier">envelope</span><span class="special">()</span></code> function. But to keep it simple lets just
generate some boxes manually and insert them into the R-tree by using <code class="computeroutput"><span class="identifier">insert</span><span class="special">()</span></code>
method.
</p>
<p>
</p>
<pre class="programlisting"><span class="comment">// create some values</span>
<span class="keyword">for</span> <span class="special">(</span> <span class="keyword">unsigned</span> <span class="identifier">i</span> <span class="special">=</span> <span class="number">0</span> <span class="special">;</span> <span class="identifier">i</span> <span class="special"><</span> <span class="number">10</span> <span class="special">;</span> <span class="special">++</span><span class="identifier">i</span> <span class="special">)</span>
<span class="special">{</span>
<span class="comment">// create a box</span>
<span class="identifier">box</span> <span class="identifier">b</span><span class="special">(</span><span class="identifier">point</span><span class="special">(</span><span class="identifier">i</span> <span class="special">+</span> <span class="number">0.0f</span><span class="special">,</span> <span class="identifier">i</span> <span class="special">+</span> <span class="number">0.0f</span><span class="special">),</span> <span class="identifier">point</span><span class="special">(</span><span class="identifier">i</span> <span class="special">+</span> <span class="number">0.5f</span><span class="special">,</span> <span class="identifier">i</span> <span class="special">+</span> <span class="number">0.5f</span><span class="special">));</span>
<span class="comment">// insert new value</span>
<span class="identifier">rtree</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span><span class="identifier">std</span><span class="special">::</span><span class="identifier">make_pair</span><span class="special">(</span><span class="identifier">b</span><span class="special">,</span> <span class="identifier">i</span><span class="special">));</span>
<span class="special">}</span>
</pre>
<p>
</p>
<p>
There are various types of spatial queries that may be performed, they can
be even combined together in one call. For simplicity, we use the default
one. The following query return values intersecting a box. The sequence of
<code class="computeroutput"><span class="identifier">Values</span></code> in the result is not
specified.
</p>
<p>
</p>
<pre class="programlisting"><span class="comment">// find values intersecting some area defined by a box</span>
<span class="identifier">box</span> <span class="identifier">query_box</span><span class="special">(</span><span class="identifier">point</span><span class="special">(</span><span class="number">0</span><span class="special">,</span> <span class="number">0</span><span class="special">),</span> <span class="identifier">point</span><span class="special">(</span><span class="number">5</span><span class="special">,</span> <span class="number">5</span><span class="special">));</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">value</span><span class="special">></span> <span class="identifier">result_s</span><span class="special">;</span>
<span class="identifier">rtree</span><span class="special">.</span><span class="identifier">query</span><span class="special">(</span><span class="identifier">bgi</span><span class="special">::</span><span class="identifier">intersects</span><span class="special">(</span><span class="identifier">query_box</span><span class="special">),</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">back_inserter</span><span class="special">(</span><span class="identifier">result_s</span><span class="special">));</span>
</pre>
<p>
</p>
<p>
Other type of query is k-nearest neighbor search. It returns some number
of values nearest to some point in space. The default knn query may be performed
as follows. The sequence of <code class="computeroutput"><span class="identifier">Values</span></code>
in the result is not specified.
</p>
<p>
</p>
<pre class="programlisting"><span class="comment">// find 5 nearest values to a point</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">vector</span><span class="special"><</span><span class="identifier">value</span><span class="special">></span> <span class="identifier">result_n</span><span class="special">;</span>
<span class="identifier">rtree</span><span class="special">.</span><span class="identifier">query</span><span class="special">(</span><span class="identifier">bgi</span><span class="special">::</span><span class="identifier">nearest</span><span class="special">(</span><span class="identifier">point</span><span class="special">(</span><span class="number">0</span><span class="special">,</span> <span class="number">0</span><span class="special">),</span> <span class="number">5</span><span class="special">),</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">back_inserter</span><span class="special">(</span><span class="identifier">result_n</span><span class="special">));</span>
</pre>
<p>
</p>
<p>
At the end we'll print results.
</p>
<p>
</p>
<pre class="programlisting"><span class="comment">// display results</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"spatial query box:"</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">bg</span><span class="special">::</span><span class="identifier">wkt</span><span class="special"><</span><span class="identifier">box</span><span class="special">>(</span><span class="identifier">query_box</span><span class="special">)</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"spatial query result:"</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="identifier">BOOST_FOREACH</span><span class="special">(</span><span class="identifier">value</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span><span class="special">,</span> <span class="identifier">result_s</span><span class="special">)</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">bg</span><span class="special">::</span><span class="identifier">wkt</span><span class="special"><</span><span class="identifier">box</span><span class="special">>(</span><span class="identifier">v</span><span class="special">.</span><span class="identifier">first</span><span class="special">)</span> <span class="special"><<</span> <span class="string">" - "</span> <span class="special"><<</span> <span class="identifier">v</span><span class="special">.</span><span class="identifier">second</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"knn query point:"</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">bg</span><span class="special">::</span><span class="identifier">wkt</span><span class="special"><</span><span class="identifier">point</span><span class="special">>(</span><span class="identifier">point</span><span class="special">(</span><span class="number">0</span><span class="special">,</span> <span class="number">0</span><span class="special">))</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="string">"knn query result:"</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
<span class="identifier">BOOST_FOREACH</span><span class="special">(</span><span class="identifier">value</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">v</span><span class="special">,</span> <span class="identifier">result_n</span><span class="special">)</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">cout</span> <span class="special"><<</span> <span class="identifier">bg</span><span class="special">::</span><span class="identifier">wkt</span><span class="special"><</span><span class="identifier">box</span><span class="special">>(</span><span class="identifier">v</span><span class="special">.</span><span class="identifier">first</span><span class="special">)</span> <span class="special"><<</span> <span class="string">" - "</span> <span class="special"><<</span> <span class="identifier">v</span><span class="special">.</span><span class="identifier">second</span> <span class="special"><<</span> <span class="identifier">std</span><span class="special">::</span><span class="identifier">endl</span><span class="special">;</span>
</pre>
<p>
</p>
<h4>
<a name="geometry.spatial_indexes.rtree_quickstart.h0"></a>
<span class="phrase"><a name="geometry.spatial_indexes.rtree_quickstart.more"></a></span><a class="link" href="rtree_quickstart.html#geometry.spatial_indexes.rtree_quickstart.more">More</a>
</h4>
<p>
More information about the R-tree implementation, other algorithms and queries
may be found in other parts of this documentation.
</p>
</div>
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<td align="right"><div class="copyright-footer">Copyright © 2009-2015 Barend Gehrels, Bruno Lalande,
Mateusz Loskot, Adam Wulkiewicz, Oracle and/or its affiliates<p>
Distributed under the Boost Software License, Version 1.0. (See accompanying
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>)
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