Introducing the Spatial Analyst Supplemental tools

With the introduction of the capability for sharing custom tools in ArcGIS 10.1, we here in the Spatial Analyst team have endeavored to provide some new functionality as a collection of script tools. These tools can be used as-is for the applications they are identified for, or you can modify them to handle specific use cases that you might have.

The following sections describe what each of these sample tools do and how they fit in with the rest of the available tools.

Create Dendrogram tool

In  the process of classifying multiband raster input using the Class Probability or Maximum Likelihood tools, a signature file is a required input.  In order to have a good classification, ideally there should be little overlap between the individual clusters in the multidimensional attribute space of the input bands.

By analyzing the statistics contained in a signature file, the Dendrogram tool in Spatial Analyst depicts the relationships between the classes graphically in a specially-formatted ASCII text file.  The Create Dendrogram tool gives you the option to output the dendrogram to a PDF file, which gives a better graphic result. By analyzing at the dendrogram, you can determine if the clusters identified in the signature file are distinct enough to give a good classification result.

Draw Signatures tool

When classifying raster images, better results are obtained when there is minimal overlap between the classes. Similar to the Dendrogram tool described above, the Draw Signatures tool provides a way to visualize relationships between the classes, but instead of representing them as a line diagram, this approach displays the class signatures as a series of ellipses.  The ellipses outline the boundary of the sample distribution defined by a specified number of standard deviations.

(Long time users may remember the nature of this output as being similar to that of the DrawSig command in ArcINFO Workstation)

Erase Raster Values tool

Have you ever wanted to just replace certain cells in a raster without having to go through t a sequence of Con, SetNull and other operations?  With the Erase Raster Values tool, you can simply provide an input (feature or raster) that defines the areas of cells you want to change, and then specify if you want those cells to become NoData or some other value in the output raster.

Filled Contours tool

Contours are lines that connect locations of equal value on a raster surface dataset, also known as isolines. They are useful for making areas of rapid change in the phenomena being mapped more apparent and easier to see.

The Filled Contours tool creates a polygon feature class of filled contours from the raster surface.  As compared to regular contour lines, filled contour polygons can be used to easily find the area of elevation values between two particular elevation contours, or quickly summarize all the vegetation types within each contour range.

Maximum Upstream Elevation tool

One type of analysis that agencies like the USGS may perform is to model the potential debris flow an extreme rain event might cause over a mountainous terrain after a wildfire has burned through a portion of an old growth forest.  The Maximum Upstream Elevation tool creates a result that is useful to this process. It uses an elevation raster and a flow direction raster to generate an output raster of the maximum upstream elevation raster along the longest upstream flow path for each cell.

Peak tool

A well-known tool used in hydrological analysis is the Sink tool, which identifies the locations of sinks (localized depressions where all neighboring cells are higher than a particular cell, or group of cells), used in the process of creating a depressionless DEM for further analysis.  The mechanism used for that tool can be applied in such a way to provide essentially the inverse of the result, which would be the locations of all of the localized high points, or peaks, on the surface raster.  The Peak tool takes an input surface raster and outputs a raster with unique cell values for each of the peaks, as well as an optional point feature output.

Storage Capacity tool

The Storage Capacity tool can be used to generate a table of water surface elevations, and corresponding storage capacities, for a given surface raster that represents a reservoir or any other terrain surface. In addition to a table, an optional report can be created that provides tables and graphs of the stage-area and stage-volume relationships for a specified study area. These relationships can then be used for computing storage parameters at different stage elevations of a detention facility or a naturally occurring reservoir.

Tabulate Area 2 tool

The original Tabulate Area tool calculates cross-tabulated areas between two datasets.  However, if the input zones have any overlap, those features will be flattened down into one layer before performing the operation.  This new Tabulate Area 2 tool offers an improvement over the original tool by handling overlapping polygons in feature zone input.

Viewshed Along Path tool

Ordinarily, visibility is determined based on a full 360 degree field of view for each of the specified observer locations.  However, sometimes it would be helpful to constrain the field of view to smaller angle for an observer that moves along a path through a landscape.  For example, imagine being the driver of a parade float or an armored vehicle with a very limited viewport to look out of.  The new Viewshed Along Path tool creates an output that can give an indication of areas of concern along a planned route where the visibility may be of some concern.

Zonal Statistics as Table 2 tool

The original Zonal Statistics as Table tool summarizes into a table the values of a raster within the zones of another dataset.  However, if the input zones have any overlap, those will be flattened down into one layer before performing the operation.  This new Zonal Statistics as Table 2 tool processes the input in a different way, preserving the overlapping nature of zonal inputs.

Downloading and installing

The Spatial Analyst Supplemental Toolbox is available for download here:

Once you’ve downloaded the file to your machine, extract the contents of the zip file.  Then, in Catalog, navigate to the location you extracted the files to. You should now see the Python toolbox containing the Script tools .

(Note that the samples are geared for ArcGIS version 10.1 and beyond.)

Update for 10.1 SP1

In order to support the use of keywords for parameter datatypes that was introduced in ArcGIS 10.1 SP1, the toolbox has been updated to version 1.1.  One of the benefits of this change is better support for different locales.

The tools can still be used with ArcGIS 10.1 without the SP1 service pack, but some small alterations need to be made to the python scripts.  Simply follow the instructions contained in the ReleaseNotes.txt file in the download.

Version history

About the author

Juan is a Product Engineer and Documentation Lead on the Spatial Analyst team.

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