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I have been digitising a historical map which contains large areas called townlands, filled by smaller areas called fields. I digitised both as two separate vector layers, both polygons.

When digitised the field layers I snapped them to the townland boundaries where the townlands and fields shared a boundary. Unfortunately, I managed to shift the field layer by accident so now the fields and the townlands don’t overlap. Is there a topological function to fix this? To snap one layer of polygons back to another?

I tried v.clean in the GRASS module but this only appears to work for cleaning within one layer.

  • In FME, there is a transformer called Snapper which would make your polygons snap. – U2ros Sep 6 '12 at 10:57
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If you have access to ArcGIS 10 you could try the Integrate (Data Management) tool:

http://help.arcgis.com/en/arcgisdesktop/10.0/help/index.html#//00170000002s000000

  • Don't suppose you know the equivalent of this operation in QGIS/Grass? – geotheory Aug 12 '14 at 12:53
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I know you are looking for a solution with qgis: there is a plugin for qgis "affin transformation", where you can enter the following values: Scale, rotation, translation both for x and y

But here I recommend to give the free openjump a try: use werkzeuge (in English: tools) -transformiere (transform) transformieren... (transform ..) you can now draw easliy as many "shifting-vectors" you need on your map-canavas to to do the required transformation/warping

  • the openjump tool looks good (not tried it--will involve installing yet another GIS tool :-)), but again not as easy as ShapeWarp. In SW, one could just click source and destination points, and it would gather the points and compute the trasnformation (just as in ERDAS). Any thoughts? – Sharad Mar 19 at 6:48
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    there is a qgis plugin vector-bender - I did not try it myself - but it looks promising, you should give it a try, if you dont want to install openjump – Kurt Mar 19 at 19:11

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