Spatial Join tool, sum of valus of features from join dataset not working

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04-05-2013 09:17 AM
JohnTangenberg
New Contributor
I am having a problem with the Spatial Join tool (Tool box) at 10.0 SP5 ArcInfo, In the past I have used the tool to aggregate data from many small polygons to larger overlapping polygons through the field map  window setting the field to "Sum" and using JOIN_ONE_TO_ONE, resulting in a output that had the summation of the smaller polygons in the larger ones. In this case I am joining features "That have their center in" the Target feature.

Recent attempts at this have failed I end up with a join count of  1 and the values are not summed it only seems to count the 1st feature. my processing time is very short too so I know that it is not properly operating.

Attached is an image of the dialog box.

[ATTACH=CONFIG]23252[/ATTACH]

John Tangenberg
GIS Analyst
Council for Watershed Health
700 N. Alameda Street
Los Angeles, CA 90012
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1 Reply
MatthewPayne
Esri Contributor
Hi John,

The reason that "Have their Center In" does not give you the SUM of the smaller polygons is because this match option matches the join features if a target feature's center falls within them.  Basically put, if a larger polygon's centroid falls into a smaller polygon, that smaller polygon will be joined.  Here is the text from the help:

"HAVE_THEIR_CENTER_IN�??The features in the join features will be matched if a target feature's center falls within them. The center of the feature is calculated as follows: for polygon and multipoint the geometry's centroid is used, and for line input the geometry's midpoint is used."

So if you have an instance where there is not a smaller polygon existing where the larger polygon's centroid is, you would actually not get a match.  Hope this helps to clarify the behavior you are experiencing.

Matt
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