n the catchment area will be included in the returned
SpatialPolygonsDataFrame but will not be adjusted for the proportion within
the catchment area.</p></td>
    </tr>
    <tr>
      <th>distance</th>
      <td><p>Defines the size of the catchment area as the distance
around the targetlayer in the units of the projection
(default = 500 metres)</p></td>
    </tr>
    <tr>
      <th>projection</th>
      <td><p>The proj4string used to define the projection to be used
for calculating the catchment areas or a 