e>: coordinates of raster cell centers.</p></li>
<li><p><code>cell_number</code>: integer indicating the cell number.</p></li>
<li><p><code>layer_cell</code>: a unique ID for the cell within the layer in the format
<code>"layer-cell_number"</code>.</p></li>
<li><p><code>intensity</code>: maximum cell value across layers divided by the maximum
value across all layers and cells; mapped to alpha level.</p></li>
<li><p><code>specificity</code>: the degree to which intensity values are unevenly
distributed acros