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I am using ArcGIS-10.3.1. I have a feature layer that includes total population by census tract (and includes lots of other info like shape length, shape area, population density, etc.). I have an 11-km square polygon drawn on the map (just using the ArcMap drawing tool). I want to know the total population that resides within the 11-km square. The square includes some whole census tracts within it, but cuts across some others.

I assumed I could use the Clip tool somehow, but I'm unsure if it's even possible to clip a feature layer based on a polygon. And, I'm unsure how to turn the polygon into a feature layer to then use it with the Clip tool.

Any ideas on how I could do this? I'm a complete beginner - I can make maps, but don't know how to use Tools well.

  • Yes, you can clip with the Clip tool resources.arcgis.com/en/help/main/10.2/index.html#//… just make sure it's the analysis tool and not the management tool (which clips rasters).. As for population you can approximate by applying a density (population / area) for the to be clipped census tracts then estimate the population for the clipped area by multiplying the clipped area by the density. This of course is an estimate and not accurate, there is a chance that the bulk of the dwellings are on one end/side of the tract but there is no way to account for that. – Michael Stimson Aug 22 '17 at 21:05
  • I would recommend as a complete beginner in ArcGIS to do some of the 'free' online courses from Esri to get a basic understanding of some of the more common tools available.. You don't need a feature layer to use clip, you can run it from catalog with a feature class; the help says the parameters are in_features, clip_features, out_feature_class which can be feature layers (layers in ArcMap with vector data) or feature classes (like shapefiles, geodatabase feature classes etc.). – Michael Stimson Aug 22 '17 at 21:09
  • In drawing toolbar use convert graphic to feature – FelixIP Aug 22 '17 at 22:19
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You can use Spatial Join in order to Sum the specific population Field on Intersect. As Target Feature select your 11-km square and as join Feature select the population layer.

Otherwise you can convert population layer into point feaure layer (centroid for each dwelling unit) and afterwards use Spatial Join with the same specifications as mentioned above.

Another solution would be to use the Clip tool and in the export file create a new field in the type tab select double or float (for decimal numbers). Then right click and calculate the reshaped population units area. Finally create a new field (short or long integer) and multiply the ratio of the new area divided by the old area with population density to find population in the 11-km squared area. (new area/old area)*population density

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