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@@ -622,17 +622,17 @@ Topology general characteristics:
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- the format is topological (areas build from boundaries)
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- currently only 2D topology is supported
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-Topology is written for native format while pseudo-topology (boundaries
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-constructed from polygons) is written for OGR sources, see
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-<tt>v.external</tt> module.
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+Topology is written for native GRASS vector format; in case of
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+linked OGR sources (see <tt>v.external</tt> module), only
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+pseudo-topology (boundaries constructed from polygons) is written.
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The following rules apply to the vector data:
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- Boundaries should not cross each other (i.e., boundaries which would
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cross must be split at their intersection to form distict boundaries).
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- Lines can cross each other, e.g. bridges over rivers.
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+ On the contrary, lines can cross each other, e.g. bridges over rivers.
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- Lines and boundaries share nodes only if their endpoints are identical.
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- Lines or boundaries canbe forced to share a common node by snapping
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+ Lines or boundaries can be forced to share a common node by snapping
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them together. This is particulary important since nodes
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are not represented in the coor file, but only implicitly as
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endpoints of lines and boundaries.
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Markus Neteler