# Difference between revisions of "Vector topology cleaning"

From GRASS-Wiki

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'''Q:''' How about self-intersecting lines and boundaries? | '''Q:''' How about self-intersecting lines and boundaries? | ||

− | '''A:''' In the GRASS topological model self-intersecting lines are allowed, self-intersecting boundaries are not. | + | '''A:''' In the GRASS topological model self-intersecting lines are allowed, self-intersecting boundaries are not. Self-intersecting lines are ok e.g. for {{cmd|v.net}} modules, e.g. to represent a bridge of a secondary road over a highway. |

− | Self-intersecting lines are ok e.g. for {{cmd|v.net}} modules, e.g. to represent a bridge of a secondary road over a highway. | ||

Note: There are some modules that do not like self-intersecting lines, e.g with {{cmd|v.buffer}} problems are expected. | Note: There are some modules that do not like self-intersecting lines, e.g with {{cmd|v.buffer}} problems are expected. | ||

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+ | === See also === | ||

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+ | * [[Vector topology]] | ||

[[Category:FAQ]] | [[Category:FAQ]] | ||

[[Category:Vector]] | [[Category:Vector]] |

## Revision as of 16:39, 6 December 2011

**Q:** How can I patch to fitting area maps with have been digitized separately and correct the topology? I observe that the shared polygon boundaries do not perfectly match...

**A:** You can use v.clean for this.

Tools to consider:

- TBD
- ...

**Q:** How about self-intersecting lines and boundaries?

**A:** In the GRASS topological model self-intersecting lines are allowed, self-intersecting boundaries are not. Self-intersecting lines are ok e.g. for v.net modules, e.g. to represent a bridge of a secondary road over a highway.

Note: There are some modules that do not like self-intersecting lines, e.g with v.buffer problems are expected.