How to split points by polygon using ArcGIS Desktop?

Question

I am looking for a way to split points by a county polygon feature class. The attached image shows two feature classes: one composed of points and the other a county polygon feature class. The split tool would be ideal if it allowed points. I would prefer a clean output without additional fields added to the point attributes. Additionally, I would like to have the county name from the polygon feature class defining the new point feature classes (e.g. Kiowa, Clark, Comanche). I appreciate any solutions and advice.

For this example, the final product should be three point feature classes named "Kiowa", "Clark" and "Comanche" produced from one, larger point feature class. An automated solution would be ideal, as I have many, many merged point FCs over dozens of counties to work with (approximately spanning the state of KS).

Answer 1

After using Spatial Join or Intersect to get the County name attribute onto each point, try using Dan Patterson's Split Layer by Attributes tool available on the Geoprocessing Model and Script Tool Gallery.

Alternatively you could use ModelBuilder to automate this using a different approach involving Select Layer by Location (click thumbnail for full image).

Lifted from this thread on the ESRI forums: Batch Selecting by Location and Exporting Shapefiles

Answer 2

Much easier to use the intersect command.
Turn off unwanted fields.
1. Intersect to a new output.
2. Join the output with the original oid.
3. Calculate a new field with the cnty name.

Check out ettools for some enhanced versions of spatial join and split by location.

Answer 3

From what I read I would just run an overlay (ArcToolbox Analysis Tools - Overlay - and either Identity, Intersect, or Spatial Join) of your points with a county polygon dataset. In ArcMap you could limit the fields displayed in the county layer to the field with the county name, and only that field would be added to the result. If even that added field is too much, calculate its values into the matching field in the points table and then delete the added field.

Answer 4

Using Python you can loop a "Select Layer By Location" to grab the points that overlap each countie, and then save it as a Shapefile. It would be something like this:

import arcgisscripting
# starts geoprocessing
gp = arcgisscripting.create()
gp.OverWriteOutput = 1

# Variable iniciation
points = u"Path for your point shape"
counties = u"Path for counties shape"
outDir = u"path for output directory"

#Load points as a layer
gp.MakeFeatureLayer(points, "points")

# Go county by county
rows = gp.searchcursor(counties)
row = rows.next()

# loop County by county overlap
while row.countyName: #adapt to your countie table of attributes
    # Make a layer from the feature class
    gp.MakeFeatureLayer(counties, "counties lyr", "[countieName]='" + row.countieName + "'")
    # Select all points that intersect the current countie polygon
    gp.SelectLayerByLocation(points, "intersect", "counties_lyr", 0, "new_selection")
    outSHP = outDir + row.counties + u".shp"
    gp.CopyFeatures_management(points, outSHP)
    print(outSHP)
    row = rows.next()
 # End of loop

 del rows, row, gp

 #END

I have not test it, You probably have to adapt it to your case.

Edit: Changed Select_analysis by CopyFeatures_management following @blah238 advice.

Answer 5

There is now an eLearning video tutorial (not free, but relatively cheap) called Using ArcPy Cursors to Split by Attribute and Location that includes showing how to:

Write a Python script to split one feature class using a polygon feature class into one feature class per features found within each of its polygon locations

I think it addresses the requirements of this question.

Disclaimer: I am the author and presenter of this eLearning video tutorial