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Pairwise erase vs Erase

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09-27-2023 05:44 AM
gapps
by
New Contributor

Pairwise Erase vs Erase Tool
i used both of them for the same data set and got different results!
so i tried to understand why, reading the tools description:

The Pairwise Erase tool is similar to the Erase tool in that geometric intersections are computed, but it is different in that intersections are computed on pairs of features rather than all combinations of features. This tool is efficient in situations in which the input or erase feature classes contain large numbers of densely packed features.

do i understand right, that the Erase tool is the more correct since it erases every feature with every feature ("all combinations of features") while pairwise only uses pairs so it misses some features entirely?

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DanPatterson
MVP Esteemed Contributor

Well if you can get your head around the illustrations in Pairwise Intersect,then the principle is the same,

How Pairwise Intersect works—ArcGIS Pro | Documentation

In the standard Intersect (or Erase) tool, an intersection between the overlay feature is determined with the first feature that it overlaps, then the second etc, then those intersections are intersected with the other intersections resulting in many possible output shapes as shown in the first figure.  The pairwise intersect (or erase) just considers the overlapping feature with each intersecting feature in turn and not any other intersections with their resultant.

Stare and the images and the results of your findings and I hope that it will eventually make sense


... sort of retired...
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gapps
by
New Contributor

english is not my first language so correct me if i understood wrong:
so Erase is the correct Tool to use if i want nothing in the output data to intersect each other?

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DanPatterson
MVP Esteemed Contributor

Erase will continue to erase through a stack of overlapping polygons.

Pairwise Erase will only erase by pairs through a stack of overlapping polygons, the resulting "hole" can conceivably have a different shape than the standard Erase tool

Perhaps you need to show what you are working with and the result of the different erase trials so people can help you interpret what you are seeing


... sort of retired...
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gapps
by
New Contributor

i just found a new tool: Overlay Layers where i can also erase. i am using this for the moment to see what results i get from there.

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