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I have 2 polygon datasets. One is county-owned parcels within a county. The other is a land cover dataset that I have exported to only contain the areas that are forested. I would like to select from the parcel layer those parcels that are at least 50% covered by the forested areas polygon.

How could I achieve this using ArcGIS Desktop?

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    I would start with calculating the original area of the parcels, followed by a union with the forest layer. Then remove the parts that don't overlap, then calculate the new area of the parcels. Divide the new areas by the original areas x 100 to get the percentage. Join the percentage back to the original parcel layer, select all parcels with percentage > 50 – jbalk Dec 4 '18 at 20:06
  • I appreciate the response. I need to clip my forested areas to a smaller area because at the moment there are too many polygons, and trying to delete the parts that don't overlap (after the union) results in ArcGIS freezing up on me. I'm sure once I get that straightened out, your method will provide me with the desired outcome, so thank you. – TylerL Dec 6 '18 at 14:15
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    You're welcome. Sorry I don't have time to formulate a proper answer. One thing that may help is that the Union result will have new attributes called FID_ParcelLayer and FID_ForestLayer (or whatever you layers are named). Where the parcels do not overlap the forest layer, the FID_ForestLayer will be -1 and the FID_ParcelLayer will be anything other than -1. You should be able to select/query them based on that. – jbalk Dec 6 '18 at 15:57
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Use INTERSECT with your parcels and your forest, then do a summary table that gives you total area for each parcel ID. This will be the the forested area. Then join that summary table back to the original parcels so that you can work with one record for each parcel. Calculate the percentage by diving forested area by original area.

Relative to the method in the comments on the original question, this saves you steps that will eliminate having to delete a large number of polygons in an edit session.

[Edit added later:] There's an even better way, if you have an advanced license at version 10.3 or higher. It's the Tabulate Intersection tool. Your parcels would be the "zone" features and your forest polygons would be the "class" features. Make sure that your zone field is a unique parcel ID. "Class field" is optional, so if you don't supply one, presumably the whole forest layer will be considered all one class, which is what you want. The result will be a table with a record for each parcel ID, and the area and percentage covered by forest calculated for you. All in one step, just what you need.

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