I am a college student working on an independent research project and I am trying to figure out how many points fall within a polygon.

I am examining the impacts of zoning in the Great Barrier Reef and I am currently focusing on coral bleaching occurrences.
I have already created a map in ArcMap with a layer for recorded coral bleaching (symbolized by levels of severity) and a layer file of the different zones (general use, conservation park, etc).

We already created a count field and a spatial join between the point shapefile (coral bleaching) and the polygon shapefile (zones). The problem we are having is that when we try to group or summarize the points to the zones the program is recognizing each area (over 100) as its own zone instead of grouping the zones together. For example if there are 45 specific areas that are classified within the general use zone the computer counts all 45 areas instead of lumping them together under general use. Right now it is stating that each zone only has 1 value within it.

Question- What tools in ArcMap would be able to group the polygons together based on a common field (zone_) even with 1000 different values.

The scenario is: Given a layer bleaching occurs and a layer of zone boundaries by zone-use type, calculate/summarize the number of bleaching occurrences in within each zone.

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    Hi, and welcome to GISse! Please edit your question to include a tabular example of the data you are trying to group. This will help us better understand your problem. Also, what software are you using, and any other detail you think relevant. Generally, more is better! – Get Spatial Mar 21 '17 at 17:59
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    Multiple options in R exists to count the number of points within a polygon. Please rephrase your question to ask one question at a time. gis.stackexchange.com/questions/110117/… – Vijay Ramesh Mar 21 '17 at 18:07
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    Your title and body don't appear to be from the same question. – Vince Mar 21 '17 at 23:23

The tool you are looking for in most GIS apps is called Dissolve (not sure what software you are using). You should first dissolve the polygon layer by the group/zone field. Then, spatially join the point layer to the polygon layer. This should give you a join_count column (using ArcGIS Desktop in the polygon layer) summarizing how many points are within each unique polygon/zone.

  • @Keanah Turner Maybe try first multipart to single part tool, then repair geometry too, then dissolve. I would go with splitting data up too like you have if the data is large. – artwork21 Mar 23 '17 at 13:36

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