Moving Window Point Analysis Tool

Download tool: Point_Analysis.tbx

The Moving Window Point Analysis tool is a new Arc Toolbox command, implemented by importing a toolbox (.tbx) file into the users’ standard Arc Toolbox. This is accomplished by right clicking on the standard Arc Toolbox and selecting “Add Toolbox”.

The Moving Window Point Analysis tool requires no Administrative privileges, setup/install programs or installation of any files other than the .tbx file itself – it is completely self-contained.  ArcGIS 10 is required to utilize the tool.

Once the toolbox is imported the command is ready to use and will function just as any other Arc Toolbox command.
This tool allows users to identify sample points that are within neighborhoods of focal points, for multiple neighborhood sizes. This is the first procedural step in a number of geostatistical analyses (e.g. semivariance analysis, fractal analysis, lacunarity).

The tool takes an input point shapefile and “moves” point by point executing a series of buffers of user-defined sizes around each point. The tool counts the number of points which fall into each buffer and also sums the values of a user-provided “Count Field” (for instance, a count of organisms found at each site) for all points falling in a buffer. These calculations are stored in new fields added by the tool to a copy of the original shapefile.

To use the tool, the user needs an input a POINT shapefile with an INTEGER field that is can be used as a Count Field (for instance, the number of organisms found at each site). Within the Point Analysis Toolbox, navigate to and select the “Input Shapefile” and the “Count” field. Next, select the “Scratch Workspace” – this should be an EMPTY directory with NO SPACES in the path. It is suggested to create a new “Scratch Workspace” with each run (e.g. “C:\pa_temp”). Lastly, enter and add (using the “+” sign) the radius for each of the buffers to be performed on each point in the dataset.

Notes on Using the Tool:

The output shapefile will be named the same as the input shapefile with a “_pa” appended to the end of the filename (input = test.shp, output = test_pa.shp) . The output shapefile will reside in the same directory as the input shapefile. The input shapefile will not be modified.

UNIQUE buffer radii MUST be entered. Entering the same radius twice will cause the program to fail while trying to add a field which already exists.

The units for entering buffer radii are MAPUNITS. Check the layer’s projection to identify what the units are.

The “focal” point (the current point being buffered) will be included in the count of points within each buffer and the value of the “focal” point’s “Count” field will be included in the sum of the “Count” field values within each buffer.

The fields which are added to the original shapefile will be named B{buffer distance}p (for example: B1000p) for the count of the number of points which fall in each buffer, and B{buffer distance}c (for example: B1000c) for the sum of the “Count” field.

The “Scratch Workspace” is a temporary working area and MUST be an empty directory with NO SPACES in the path. It is suggested to use a new temporary directory for each run (e.g. “C:\pa_temp”). This can be accomplished by using the “New Directory” icon when populating the “Scratch Workspace” dialog box. The program writes a large number of files to the “Scratch Workspace” and then cleans up after itself if it runs successfully, leaving only the empty directory and an empty INFO subdirectory. If, however, the program fails, files may be left in the “Scratch Workspace”.

Below is an example of using the program on a 15-site shapefile and the resulting calculated fields:

Point of contact: Douglas A. Olsen