# Site selection in ArcMap?

Within a large dataset that contains information on location and attributes of forest plots, I need to identify treatment and reference plots for my research.

I ran into problems with reference plot selection. I'm using a pairwise approach, so each treatment plot is to be paired with a reference plot. The criteria for reference plots are:

1. of the same forest type as a treatment plot; 2. located at a minimum distance from a treatment plot.

This means that for each treatment plot, I need to create a subset of plots of the same forest type (a field in the dataset) and then select a plot that is nearest to the treatment plot. Also, I need to make sure that a certain reference plot represented only once.

I have over 500 treatment plots.

How can I do this in in ArcMap?

• If ArcMap does not provide a suitable solution please ask about R in a separate question. – PolyGeo Jan 7 '16 at 11:11

You can accomplish this in ArcMap.

1. Create a buffer around each plot with the minimum distance set
2. Select all reference plots within the buffer perimeter (select-by-location)
3. Export the selected plots
4. Use the forest type attribute as parameter for symbology

Now you have an overview of all the reference plots within a minimum distance of the treatment plots.

• I might set up a maximum allowed distance between a treatment and reference plot by creating buffers or within Near tool. However, I can't see how it will really help me. The thing is that a minimum distance is not fixed; it will be different for each plot pair. Treatment plots represent various forest types, so for each treatment plot I need to select different subset of potential reference plots. I wonder if I can create some kind of loop to do it. Thanks. – Marina Golivets Jan 7 '16 at 14:40
• Can you be more specific about the distance between the reference and treatment plots? – Stefan Jan 7 '16 at 14:43
• The dataset is a grid of point features. So far my criteria for plot pairs has been "to be as close as possible". It means that in some cases I might end up with a 2-km distance between a pair of plots, while in other cases the distance will be 10 km or so. – Marina Golivets Jan 7 '16 at 14:51
• The NEAR Analysis tool is something you can use. resources.arcgis.com/en/help/main/10.1/index.html#//… – Stefan Jan 7 '16 at 14:56