Overlaying two polygons by their centroids?

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04-03-2018 07:49 AM
JennaWatson
New Contributor

I have two polygons and I calculated the centroid for each. Now I want to overlay the polygons by their centroid so that they point at which they line up is their centroid. However, when I go to edit each polygon and try to drag it over to line its centroid up with the other polygon's centroid, the centroid does not move with it. I have even tried creating a new shape file and drawing a polygon over the centroid point and then merging the centroid polygon with the larger polygon, but they still won't move together in editor! Is there any way to tie/glue/stick/join/etc a polygon's centroid to its corresponding polygon so that they can be moved together? Or is there a way to overlay two polygons by their centroids? Attached is an image of the polygons that I am trying to overlay with their centroids.

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MelitaKennedy
Esri Notable Contributor

A tricksy way to solve this is to separate the polygons and centroids into separate feature classes. {roject the corresponding feature classes (AKA 2 red/2 blue) to custom azimuthal equidistant projections, centered on the centroids. Now take the "offset" one and change its coordinate system via Define Projection tool to use the other projected coordinate system. That will line them up, or you could now unproject the redefined one back to lat/lon if you want.

Another possibility would be to add a tiny hole where the centroid is, to the polygon you want to move. Move it, and erase the hole.

The centroids should be in a point feature class, not the polygon one, which is why you can't move them together.

Melita

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MelitaKennedy
Esri Notable Contributor

A tricksy way to solve this is to separate the polygons and centroids into separate feature classes. {roject the corresponding feature classes (AKA 2 red/2 blue) to custom azimuthal equidistant projections, centered on the centroids. Now take the "offset" one and change its coordinate system via Define Projection tool to use the other projected coordinate system. That will line them up, or you could now unproject the redefined one back to lat/lon if you want.

Another possibility would be to add a tiny hole where the centroid is, to the polygon you want to move. Move it, and erase the hole.

The centroids should be in a point feature class, not the polygon one, which is why you can't move them together.

Melita

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