Vector topology cleaning
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... I need clean topology.
A: You can use v.clean for this.
Tools to consider:
- snap,bpol,rmdupl,break,rmdupl,rms
- the threshold (in map units) should be very small
Example (Lat-Long):
v.in.ogr natural_earth/ne_110m_admin_0_countries.shp out=country_boundaries snap=0.0001 TODO: FIX THIS
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.
Polygon import from SHAPE file:
v.clean applied:
