[Qgis-developer] Dropping vertices at intersections

[Zoltan Szecsei]

Hi All,
I've looked at the topology plugin, but can't find what I need to do.
I've been exporting the data into Genamap and doing this with scripts, 
but it would be nice to do it in QGIS.
Anyone know of a plugin?

Quite often now we've been asked to deliver products whereby there are 
vertices placed onto graphic elements where they cross over, or end on, 
each other (in different layers (Shape files)).

eg: A road line stops at the edge of a cropfield polygon, so drop a 
vertice at that place, on the cropfield boundary. Likewise if a road 
runs through a field, but the data capture scale requires the field not 
to be split into two polygons, drop the vertice at the points where the 
road crosses over the field boundary.

Ideally this could be implemented by:

  * Check boxes to select all the layers you want to process (mixture
    between multiple polygon and line layers)
  * selecting the snapping distance (for lines that end "close enough"
    to other boundaries or lines).
  * Having a separate checkbox for "Crossover" and for "Line ends"
  * Perhaps even an option to log (create a pointfile) when lines end
    within 'X' of any boundary or line (where X is a secondary snap
    distance)
  * perhaps have an option to log (point file) where lines run parallel
    to others, within the snap distance set (maybe with even a tertiary
    snap distance)

Instead of looping through multiple snap distances, one could implement 
a checkbox to either drop the vertice, or to just mark the position 
where the vertice should have been dropped - this would be easier for 
the developer, but require the user to run the procedure multiple times, 
in order to see where "close enough" stuff lies.

Any comments?

Regards,
Zoltan


-- 

===========================================
Zoltan Szecsei PrGISc [PGP0031]
Geograph (Pty) Ltd.
GIS and Photogrammetric Services

P.O. Box 7, Muizenberg 7950, South Africa.

Mobile: +27-83-6004028
Fax:    +27-86-6115323www.geograph.co.za
===========================================

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