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I have two shapefiles: the first with a series of polygons that overlap; the second with a series of polygons that don't overlap. I need to separate the first ones according to the line of the second, keeping the overlapping polygons separated.

Graphically:

enter image description here

This is the initial situation: the shapefile contains several polygons that overlap and each polygon can be crossed by a line of a polygon that is in another shapefile (the red rectangles in the picture)

enter image description here

What I need to obtain at the end are the old polygons splitter according to the red one. In the example each polygon will be divided in two parts:

  • 1a will be the yellow on the left + the green part;
  • 1b will be the yellow on the right + the orange part;
  • 2a will be the grey on the left + the green part;
  • 2b will be the grey on the right + the orange part.

What I tried is to use the union tool and then the dissolve tool: with the first one I obtain six different polygons (one different polygon for each line that cross, no matter if it comes from the red polygon or the overlapping one).

Then I tried to dissolve indicating as "dissolve fields" the FID of the original two layers (FID_shp1 and FID_shp2) but basically nothing happened.

Any suggestion? should I use something different? I mean, is there a way to avoid that the overlapping lines became a separator and only the "red lines" are taken into consideration?


EDIT 1: Just to make the comprehension easier. This is the initial situation:

enter image description here

Each of this polygons can be crossed by other polygons that are in another shapefile

enter image description here

I need to arrive at the end at this situation

enter image description here

i.e. four different polygons that basically are the initial polygons divided by the red line of the polygons of the other shapefile.

The problem with the union tool are two-fold:

  1. The union tool take all the lines as a separator, included the ones of the overlapping polygons;
  2. Once I unified, the attributes of the second file are not copied but it will be transformed in something different (for example, all the FID of the second shapefile became -1. That's why maybe the dissolve tool doesn't work properly).
  • If you have an advance license then have a look at the Identity tool instead of the Union. – Hornbydd Nov 11 '16 at 16:31
  • The -1 values demonstrate that Union is working correctly. All the Overlay tools start with the same intermediate product; they just differ in the final output. – Vince Nov 12 '16 at 12:32
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Well, this question is little confusing..but i want to suggest what i understood from your question. If you want a separated overlapping portion, then you can use the Intersect tool from the toolbox. And if you want parts of the original polygon without the overlapping parts, then you can use Cut Polygon tool to cut the overlapping portion form the original one.

  • I try to edit the question with more clear images – Nicola Nov 11 '16 at 16:59
  • Well..then, it's a series of intersection and cut polygon actions performed one after another just like solving a mathematical expression..just be careful with which polygon to use as the input polygon and which one to use as cutting polygon...first, you can use intersection tool to get the common polygon from all the polygons..then you can use cut polygon with proper input and cutting polygon to obtain the result as desired..it includes various steps of intersection and cutting..you can also try clip analysis for this.. – Niraj Nov 14 '16 at 13:53

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