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<div class="section" id="drawing-a-map-background">
<span id="geography"></span><h1>Drawing a Map Background<a class="headerlink" href="#drawing-a-map-background" title="Permalink to this headline">¶</a></h1>
<p>Basemap includes the
<a class="reference external" href="http://www.soest.hawaii.edu/wessel/gshhs/gshhs.html">GSSH</a>
coastline dataset, as well as datasets for rivers, state and
country boundaries from
<a class="reference external" href="http://gmt.soest.hawaii.edu">GMT</a>.
These datasets can be used to draw coastlines, rivers and political
boundaries on maps at several different resolutions. The relevant Basemap
methods are:</p>
<ul class="simple">
<li><a class="reference internal" href="../api/basemap_api.html#mpl_toolkits.basemap.Basemap.drawcoastlines" title="mpl_toolkits.basemap.Basemap.drawcoastlines"><tt class="xref py py-func docutils literal"><span class="pre">drawcoastlines()</span></tt></a>: draw coastlines.</li>
<li><a class="reference internal" href="../api/basemap_api.html#mpl_toolkits.basemap.Basemap.fillcontinents" title="mpl_toolkits.basemap.Basemap.fillcontinents"><tt class="xref py py-func docutils literal"><span class="pre">fillcontinents()</span></tt></a>: color the interior
of continents (by filling the coastline polygons).
Unfortunately, the fillcontinents method doesn’t always do the right thing.
Matplotlib always tries to fill the inside of a polygon. Under certain situations,
what is the inside of a coastline polygon can be ambiguous, and the
outside may be filled instead of the inside.
In these situations, the recommended workaround is to use the
<a class="reference internal" href="../api/basemap_api.html#mpl_toolkits.basemap.Basemap.drawlsmask" title="mpl_toolkits.basemap.Basemap.drawlsmask"><tt class="xref py py-func docutils literal"><span class="pre">drawlsmask()</span></tt></a> method to
overlay an image with different colors specified for land and water regions
(see below).</li>
<li><a class="reference internal" href="../api/basemap_api.html#mpl_toolkits.basemap.Basemap.drawcountries" title="mpl_toolkits.basemap.Basemap.drawcountries"><tt class="xref py py-func docutils literal"><span class="pre">drawcountries()</span></tt></a>: draw country boundaries.</li>
<li><a class="reference internal" href="../api/basemap_api.html#mpl_toolkits.basemap.Basemap.drawstates" title="mpl_toolkits.basemap.Basemap.drawstates"><tt class="xref py py-func docutils literal"><span class="pre">drawstates()</span></tt></a>: draw state boundaries
in North America.</li>
<li><a class="reference internal" href="../api/basemap_api.html#mpl_toolkits.basemap.Basemap.drawrivers" title="mpl_toolkits.basemap.Basemap.drawrivers"><tt class="xref py py-func docutils literal"><span class="pre">drawrivers()</span></tt></a>: draw rivers.</li>
</ul>
<p>Instead of drawing coastlines and political boundaries, an image can be
used as a map background. Basemap provides several options for this:</p>
<ul class="simple">
<li><a class="reference internal" href="../api/basemap_api.html#mpl_toolkits.basemap.Basemap.drawlsmask" title="mpl_toolkits.basemap.Basemap.drawlsmask"><tt class="xref py py-func docutils literal"><span class="pre">drawlsmask()</span></tt></a>: draw a high-resolution
land-sea mask as an image, with land and ocean colors specified. The land-sea
mask is derived from the GSHHS coastline data, and there are several
coastline options and pixel sizes to choose from.</li>
<li><a class="reference internal" href="../api/basemap_api.html#mpl_toolkits.basemap.Basemap.bluemarble" title="mpl_toolkits.basemap.Basemap.bluemarble"><tt class="xref py py-func docutils literal"><span class="pre">bluemarble()</span></tt></a>: draw a NASA
<a class="reference external" href="http://visibleearth.nasa.gov/view_set.php?categoryID=2363">Blue Marble</a>
image as a map background.</li>
<li><a class="reference internal" href="../api/basemap_api.html#mpl_toolkits.basemap.Basemap.shadedrelief" title="mpl_toolkits.basemap.Basemap.shadedrelief"><tt class="xref py py-func docutils literal"><span class="pre">shadedrelief()</span></tt></a>: draw a
<a class="reference external" href="http://www.shadedrelief.com">shaded relief</a> image
as a map background.</li>
<li><a class="reference internal" href="../api/basemap_api.html#mpl_toolkits.basemap.Basemap.etopo" title="mpl_toolkits.basemap.Basemap.etopo"><tt class="xref py py-func docutils literal"><span class="pre">etopo()</span></tt></a>: draw an
<a class="reference external" href="http://www.ngdc.noaa.gov/mgg/global/global.html">etopo</a>
relief image as map background.</li>
<li><a class="reference internal" href="../api/basemap_api.html#mpl_toolkits.basemap.Basemap.warpimage" title="mpl_toolkits.basemap.Basemap.warpimage"><tt class="xref py py-func docutils literal"><span class="pre">warpimage()</span></tt></a>: use an abitrary
image as a map background. The image must be global, covering the
world in lat/lon coordinates from the international dateline eastward
and the South Pole northward.</li>
</ul>
<p>Here are examples of the various ways to draw a map background.</p>
<ol class="arabic simple">
<li>Draw coastlines, filling ocean and land areas.</li>
</ol>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">mpl_toolkits.basemap</span> <span class="kn">import</span> <span class="n">Basemap</span>
<span class="kn">import</span> <span class="nn">matplotlib.pyplot</span> <span class="kn">as</span> <span class="nn">plt</span>
<span class="c"># setup Lambert Conformal basemap.</span>
<span class="n">m</span> <span class="o">=</span> <span class="n">Basemap</span><span class="p">(</span><span class="n">width</span><span class="o">=</span><span class="mi">12000000</span><span class="p">,</span><span class="n">height</span><span class="o">=</span><span class="mi">9000000</span><span class="p">,</span><span class="n">projection</span><span class="o">=</span><span class="s">'lcc'</span><span class="p">,</span>
<span class="n">resolution</span><span class="o">=</span><span class="s">'c'</span><span class="p">,</span><span class="n">lat_1</span><span class="o">=</span><span class="mf">45.</span><span class="p">,</span><span class="n">lat_2</span><span class="o">=</span><span class="mi">55</span><span class="p">,</span><span class="n">lat_0</span><span class="o">=</span><span class="mi">50</span><span class="p">,</span><span class="n">lon_0</span><span class="o">=-</span><span class="mf">107.</span><span class="p">)</span>
<span class="c"># draw coastlines.</span>
<span class="n">m</span><span class="o">.</span><span class="n">drawcoastlines</span><span class="p">()</span>
<span class="c"># draw a boundary around the map, fill the background.</span>
<span class="c"># this background will end up being the ocean color, since</span>
<span class="c"># the continents will be drawn on top.</span>
<span class="n">m</span><span class="o">.</span><span class="n">drawmapboundary</span><span class="p">(</span><span class="n">fill_color</span><span class="o">=</span><span class="s">'aqua'</span><span class="p">)</span>
<span class="c"># fill continents, set lake color same as ocean color.</span>
<span class="n">m</span><span class="o">.</span><span class="n">fillcontinents</span><span class="p">(</span><span class="n">color</span><span class="o">=</span><span class="s">'coral'</span><span class="p">,</span><span class="n">lake_color</span><span class="o">=</span><span class="s">'aqua'</span><span class="p">)</span>
<span class="n">plt</span><span class="o">.</span><span class="n">show</span><span class="p">()</span>
</pre></div>
</div>
<p>(<a class="reference external" href="../users/figures/background1.py">Source code</a>)</p>
<ol class="arabic simple" start="2">
<li>Draw a land-sea mask as an image.</li>
</ol>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">mpl_toolkits.basemap</span> <span class="kn">import</span> <span class="n">Basemap</span>
<span class="kn">import</span> <span class="nn">matplotlib.pyplot</span> <span class="kn">as</span> <span class="nn">plt</span>
<span class="c"># setup Lambert Conformal basemap.</span>
<span class="c"># set resolution=None to skip processing of boundary datasets.</span>
<span class="n">m</span> <span class="o">=</span> <span class="n">Basemap</span><span class="p">(</span><span class="n">width</span><span class="o">=</span><span class="mi">12000000</span><span class="p">,</span><span class="n">height</span><span class="o">=</span><span class="mi">9000000</span><span class="p">,</span><span class="n">projection</span><span class="o">=</span><span class="s">'lcc'</span><span class="p">,</span>
<span class="n">resolution</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span><span class="n">lat_1</span><span class="o">=</span><span class="mf">45.</span><span class="p">,</span><span class="n">lat_2</span><span class="o">=</span><span class="mi">55</span><span class="p">,</span><span class="n">lat_0</span><span class="o">=</span><span class="mi">50</span><span class="p">,</span><span class="n">lon_0</span><span class="o">=-</span><span class="mf">107.</span><span class="p">)</span>
<span class="c"># draw a land-sea mask for a map background.</span>
<span class="c"># lakes=True means plot inland lakes with ocean color.</span>
<span class="n">m</span><span class="o">.</span><span class="n">drawlsmask</span><span class="p">(</span><span class="n">land_color</span><span class="o">=</span><span class="s">'coral'</span><span class="p">,</span><span class="n">ocean_color</span><span class="o">=</span><span class="s">'aqua'</span><span class="p">,</span><span class="n">lakes</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
<span class="n">plt</span><span class="o">.</span><span class="n">show</span><span class="p">()</span>
<span class="n">plt</span><span class="o">.</span><span class="n">show</span><span class="p">()</span>
</pre></div>
</div>
<p>(<a class="reference external" href="../users/figures/background2.py">Source code</a>)</p>
<ol class="arabic simple" start="3">
<li>Draw the NASA ‘Blue Marble’ image.</li>
</ol>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">mpl_toolkits.basemap</span> <span class="kn">import</span> <span class="n">Basemap</span>
<span class="kn">import</span> <span class="nn">matplotlib.pyplot</span> <span class="kn">as</span> <span class="nn">plt</span>
<span class="c"># setup Lambert Conformal basemap.</span>
<span class="c"># set resolution=None to skip processing of boundary datasets.</span>
<span class="n">m</span> <span class="o">=</span> <span class="n">Basemap</span><span class="p">(</span><span class="n">width</span><span class="o">=</span><span class="mi">12000000</span><span class="p">,</span><span class="n">height</span><span class="o">=</span><span class="mi">9000000</span><span class="p">,</span><span class="n">projection</span><span class="o">=</span><span class="s">'lcc'</span><span class="p">,</span>
<span class="n">resolution</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span><span class="n">lat_1</span><span class="o">=</span><span class="mf">45.</span><span class="p">,</span><span class="n">lat_2</span><span class="o">=</span><span class="mi">55</span><span class="p">,</span><span class="n">lat_0</span><span class="o">=</span><span class="mi">50</span><span class="p">,</span><span class="n">lon_0</span><span class="o">=-</span><span class="mf">107.</span><span class="p">)</span>
<span class="n">m</span><span class="o">.</span><span class="n">bluemarble</span><span class="p">()</span>
<span class="n">plt</span><span class="o">.</span><span class="n">show</span><span class="p">()</span>
</pre></div>
</div>
<p>(<a class="reference external" href="../users/figures/background3.py">Source code</a>)</p>
<ol class="arabic simple" start="4">
<li>Draw a shaded relief image.</li>
</ol>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">mpl_toolkits.basemap</span> <span class="kn">import</span> <span class="n">Basemap</span>
<span class="kn">import</span> <span class="nn">matplotlib.pyplot</span> <span class="kn">as</span> <span class="nn">plt</span>
<span class="c"># setup Lambert Conformal basemap.</span>
<span class="c"># set resolution=None to skip processing of boundary datasets.</span>
<span class="n">m</span> <span class="o">=</span> <span class="n">Basemap</span><span class="p">(</span><span class="n">width</span><span class="o">=</span><span class="mi">12000000</span><span class="p">,</span><span class="n">height</span><span class="o">=</span><span class="mi">9000000</span><span class="p">,</span><span class="n">projection</span><span class="o">=</span><span class="s">'lcc'</span><span class="p">,</span>
<span class="n">resolution</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span><span class="n">lat_1</span><span class="o">=</span><span class="mf">45.</span><span class="p">,</span><span class="n">lat_2</span><span class="o">=</span><span class="mi">55</span><span class="p">,</span><span class="n">lat_0</span><span class="o">=</span><span class="mi">50</span><span class="p">,</span><span class="n">lon_0</span><span class="o">=-</span><span class="mf">107.</span><span class="p">)</span>
<span class="n">m</span><span class="o">.</span><span class="n">shadedrelief</span><span class="p">()</span>
<span class="n">plt</span><span class="o">.</span><span class="n">show</span><span class="p">()</span>
</pre></div>
</div>
<p>(<a class="reference external" href="../users/figures/background4.py">Source code</a>)</p>
<ol class="arabic simple" start="5">
<li>Draw an etopo relief image.</li>
</ol>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">mpl_toolkits.basemap</span> <span class="kn">import</span> <span class="n">Basemap</span>
<span class="kn">import</span> <span class="nn">matplotlib.pyplot</span> <span class="kn">as</span> <span class="nn">plt</span>
<span class="c"># setup Lambert Conformal basemap.</span>
<span class="c"># set resolution=None to skip processing of boundary datasets.</span>
<span class="n">m</span> <span class="o">=</span> <span class="n">Basemap</span><span class="p">(</span><span class="n">width</span><span class="o">=</span><span class="mi">12000000</span><span class="p">,</span><span class="n">height</span><span class="o">=</span><span class="mi">9000000</span><span class="p">,</span><span class="n">projection</span><span class="o">=</span><span class="s">'lcc'</span><span class="p">,</span>
<span class="n">resolution</span><span class="o">=</span><span class="bp">None</span><span class="p">,</span><span class="n">lat_1</span><span class="o">=</span><span class="mf">45.</span><span class="p">,</span><span class="n">lat_2</span><span class="o">=</span><span class="mi">55</span><span class="p">,</span><span class="n">lat_0</span><span class="o">=</span><span class="mi">50</span><span class="p">,</span><span class="n">lon_0</span><span class="o">=-</span><span class="mf">107.</span><span class="p">)</span>
<span class="n">m</span><span class="o">.</span><span class="n">etopo</span><span class="p">()</span>
<span class="n">plt</span><span class="o">.</span><span class="n">show</span><span class="p">()</span>
</pre></div>
</div>
<p>(<a class="reference external" href="../users/figures/background5.py">Source code</a>)</p>
</div>
</div>
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