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Counting points

September 29 2010 | 0 comments
Categories: Map Data

I am a very basic, self-taught, ArcMap user. I created a map of the U.S. with locations of mining operations. Also shown are selected cities with 250 and 500 mile buffers. To count the numbers of mines within the buffers I joined the city and mine location (by county) layers and got the totals from the attribute table. I have a co-worker that did some manual counting of the dots and found that they do not match. The numbers in the attribute table are higher than the dots displayed on the map. Please advise.

Mapping Center Answer:

If you are doing a straight count, using the Select by Location function may be a good option for you. This functionality is found in the Selection tab. You will select features from the mine operations that have their centroid within the city buffers. Once you apply this you can open up the attribute table of the mines and see how many are selected.

If you want to join these two features the tool to use is the Spatial Join tool.  It transfers attributes form one feature class to another based on the spatial relationships between the features classes.

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