|
|
@@ -93,8 +93,8 @@ approximation and topographic analysis from a point or isoline file.
|
|
|
<li> point: a point; </li>
|
|
|
<li> line: a directed sequence of connected vertices with two endpoints called nodes; </li>
|
|
|
<li> boundary: the border line to describe an area; </li>
|
|
|
-<li> centroid: a point within a closed boundary; </li>
|
|
|
-<li> area: the topological composition of centroid and boundary; </li>
|
|
|
+<li> centroid: a point within a closed ring of boundaries; </li>
|
|
|
+<li> area: the topological composition of a closed ring of boundaries and optionally a centroid; </li>
|
|
|
<li> face: a 3D area; </li>
|
|
|
<li> kernel: a 3D centroid in a volume (not yet implemented); </li>
|
|
|
<li> volume: a 3D corpus, the topological composition of faces and kernel (not yet implemented). </li>
|
|
|
@@ -102,10 +102,10 @@ approximation and topographic analysis from a point or isoline file.
|
|
|
<p>
|
|
|
Note that all lines and boundaries can be polylines (with nodes in between).
|
|
|
<p>
|
|
|
-Topology also holds information about isles. Isles are located within an
|
|
|
-area, not touching the boundaries of the outer area. Isles consist of
|
|
|
-one or more areas and are used internally to maintain correct topology
|
|
|
-for areas.
|
|
|
+Area topology also holds information about isles. These isles are located
|
|
|
+within that area, not touching the boundaries of the outer area. Isles
|
|
|
+consist of one or more areas and are used internally to maintain correct
|
|
|
+topology for areas.
|
|
|
|
|
|
<P>
|
|
|
The <a href="v.type.html">v.type</a> module can be used to convert
|
|
|
@@ -126,7 +126,7 @@ Adjacent polygons can be found by <a href="v.to.db.html">v.to.db</a>
|
|
|
Many operations including extraction, queries, overlay, and export will
|
|
|
only act on features which have been assigned a category number. Typically
|
|
|
a centroid will hold the attribute data for the area between it and its
|
|
|
-boundary. Boundaries are not typically given a category ID as it would be
|
|
|
+boundaries. Boundaries are not typically given a category ID as it would be
|
|
|
ambiguous as to which area either side of it the attribute data would belong
|
|
|
to. An exception might be when the boundary between two crop-fields is the
|
|
|
center-line of a road, and the category information is an index to the road
|
Markus Metz