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Attaching individual data points to administrative boundaries

December 02 2009 | 0 comments
Categories: ArcGIS Methods

I know this is probably a really basic question. But I'm just starting out with ArcGIS and its kind of slow going.

Anyway, I did a survey all around the country (New Zealand). I now have my survey results represented on the map of New Zealand as individual points. This is fine for some data representation, but for a lot of the stuff I want to look at differences between regions.

How do I lump the survey responses into the regions that they are located within? So that I can simply have a map with the regional boundaries with different shades of colour representing certain averaged data for each region, rather than a whole bunch of individual points.

I have the GIS layer for my regional boundaries I just need to know how to get the individual points to 'stick' within a boundary so they can be analysed as groups.

Thanks for you help.

Mapping Center Answer:

This is a 3-step process:

Assign the administrative unit IDs to the survey points

To to this, use the Identity tool where the input features will be your survey points, and the identity features will be the administrative unit polygons.  Set the join attributes to be the field containing name or ID of the administrative units. It is very important that the values in this field be unique.  This will produce a new point dataset, with an additional field with the administrative unit each point belongs to.

Summarize the survey point by administrative ID

Use the Summary Statistics tool where the Input table is the the point dataset produce by the Identity tool.  The statistics field or fields will be those fields from your survey that you want summarized relative to the administrative units.  You will need to pick the fields and the summary statistic--you can also do multiple summaries for a given field, such as a sum and a mean.  The Case field will be the field containing the ID of the administrative unit.

Join the summarized data to the administrative units

Last use the Join field tool join the summary statistics table to the administrative units.  The input will be your administrative units, the join field will be the field you used for the Identity tool, and the join table will be the result of the Summary Statistics tool.  Then just pick the fields from the summary table you want to include for your maps.

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