 input grid
reference. Parent references will be a vector of <code>BNGReference</code></p>


<p>objects.</p>
    </div>
    <div class="section level2">
    <h2 id="details">Details<a class="anchor" aria-label="anchor" href="#details"></a></h2>
    <p>The BNG is structured using a hierarchical system of grid squares at
various resolutions. At its highest level, the grid divides GB into 100 km
by 100 km squares, each identified by a two-letter code. Successive levels
of resolution further subdivide the grid 