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Adding Lat-Long for the centroids of USA counties in a new point shapefile (ArcMap 10)

Software: ArcGIS - ArcEditor 9.2, 9.3, 9.3.1, 10 ArcGIS - ArcInfo 9.2, 9.3, 9.3.1, 10 ArcGIS - ArcView 9.2, 9.3, 9.3.1, 10 ArcGIS for Desktop Advanced 10.1 ArcGIS for Desktop Standard 10.1

USA counties center pointsThis is documented step-by-step and hands-on exercise on how to create XY point shapefile for the centers of USA counties (with linked basic demography and FIPS) in ArcMap 10.1. You don’t need to follow those steps (and if you don’t have ArcGIS for Desktop, you cannot) and may just grab the resulted layer file in various formats at the end of this post. Formats available are MS Excel table, CSV table with XY, zipped SHP file package, and KMZ file.

This layer is not directly shareable on ArcGIS Online, as it has more than 1000 features (3143, to be exact), we may post it there later as partial files…

If you need help with your GIS project, please, do not hesitate to contact Landviser, LLC - post comment, email info@landviser.com, or call 609-412-0555. Current complete catalog of Landviser LLC

1. Linking County shapefile with State shapefile (from 9.3 version data DVD) – to get state abbreviation in table with FIPS. Link based on State name (full).image_34_5FC33B5A

2. Export joint file as shapefile and clean table of not needed state records.

3. Download new county shapefile with 2010 demographics and 2007 farm data of ArcGIS Online. Created Point file for the centroids of a new file:

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Add X_Longitude and Y_Latitude as Double data format (6, 2) for two decimal points. 

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For both X and Y right click the column and choose “Calculate Geometry” and X or Y coordinate of Centroid respectively. Choose units as Decimal degrees.

image_thumb_4_5FC33B5Aimage_thumb_6_5FC33B5A

image_thumb_8_5FC33B5AExport to a table. In the attribute table, select Options > Export.

Specify a name and location for the new table.

Add the new table to current map.image_thumb_9_5FC33B5A

Go to your map Legend (Table of Content) and choose to display XY data:

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4. Oops! Where are the center points? If you had selected wrong projection for your original map they might all be stuck in the middle of whole USA as a tiny replica:

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You will need to go and change a projection to Geographic WGS 1984.prj

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Finally, you’re your new point data layer matches your map extent! image_thumb_14_0DB08E13

5. Now, you will need to export the Event Layer to a shapefile by right-clicking on the layer and navigating to Data > Export Data.image_thumb_17_5FC33B5A

6. Spatially Join the center point in the file created in step 6 to the data layer created in step 2. Delete duplicate fields in joint shapefile. Export as table, KML, shapefile, whatever.

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This layer is not directly shareable on ArcGIS Online, as it has more than 1000 features (3143, to be exact), we may post it there later as partial files…

If you need help with your GIS project, please, do not hesitate to contact Landviser, LLC - post comment, email info@landviser.com, or call 609-412-0555.

Current complete catalog of Landviser LLC

Registered users can download the GIS shapefiles of USA counties polygons and centroids points attached to this webpage:

(Yes, it includes Alaska too)