Converting Rasters to Polygon Features
Included in this tutorial:
Accessing the Raster to Polygon tool and reviewing its options and parameters
Running the tool with an example
Examining the results: Polygon output and attributes
Software version in examples: ArcGIS Pro 3.0.0
Tutorial Data: The tutorial includes demonstration with sample data available here.
Credits: L. Meisterlin and Varisa Tanti (2022)
This tutorial demonstrates using the Raster to Polygon tool in ArcGIS Pro, which converts raster datasets to polygon feature classes based on raster cell values (and replicates those values within the output feature class’s attribute table).
Accessing the Raster to Polygon Tool
You can access the Raster to Point tool by clicking the Geoprocessing toolbox in the main ribbon, and selecting Conversion Tools > To Raster > Raster to Polygon. You can also search for “Raster to Polygon” in the Geoprocessing search bar.
The path to opening the Raster to Polygon tool is Geoprocessing Tools > Conversion Tools > From Raster > Raster to Polygon.
Raster to Polygon Options & Parameters
the Raster to Polygon geoprocessing tool
In the Raster to Polygon dialogue box, you will see these fields: input raster, field, output polygon features, simplify polygons option, create multipart feature option, and maximum vertices per polygon feature.
Here’s a brief description of the different inputs:
Input raster: The input raster dataset. The options that appear in the drop-down menu will be the raster datasets in your project.
Field: The values from the input raster based upon which the new polygon features will be generated. (These values will also be included in the polygon feature class’s attribute table.) Adjacent cells with the same value will be combined into polygon features in the output, based on the other parameters below.
The options available from this drop-down depend on the nature of your input raster. For single-band rasters, the value associated with each cell is the only option. For multiband (or composite) rasters, a user will need to specify the value.
Output polygon features: The location and name of the output polygon feature layer
Simplify polygons checkbox: This determines if the output polygons will be smoothed into simpler shapes (checked) or conform to the input raster’s cell edges (unchecked).
Create multipart features checkbox: This specifies whether the output polygons will consist of single-part (unchecked) or multipart (checked) features.
Maximum vertices per polygon feature: Specifying a maximum vertex limit will create (subdivided) smaller polygons if this limit is reached based on the input raster’s cell values. The default (leaving the box empty) will not split the output polygons.
After specifying the different options, click Run to execute the tool.
Example Results
The tutorial’s example input raster was produced by converting the Tract layer in the Tutorial Data Standard Data Package to a raster layer using the “count_” field and reclassifying it.
Examining the Polygon Output
In the examples below, the raster layer (called Reclass_Count) was converted to a polygon feature class. The example on the left did not use the “Simplify polygons” option, while the one on the right did. You can see that without the “Simplify polygons” option, the polygons follow the raster cell outlines exactly.
the polygon feature class output with the “Simplify polygons” option checked
the polygon feature layer output with the “Simplify polygons” option not checked, resulting in smoothed edges
Additionally, contiguous cells that had the same value were grouped to produce the polygon. Those values can now be found in the “gridcode” field in the attribute table, symbolized with a purple color ramp in the image below.
Contiguous cells that had the same value were grouped to produce the new polygons.
Examining the Attributes
Examining the output feature class’s attribute table, you’ll notice that the resulting feature class has the default OBJECTID field, which is a unique ID assigned to every polygon.
the example output attribute table with the new “gridcode” field, among others
Importantly, you can also see the new field “gridcode,” which includes the corresponding cell values from the input raster. The polygons’ length and area (in the units of the input raster’s CRS, which is now the resulting feature class’s CRS) are also automatically generated.
(We can tell from the repetition of values in the gridcode field that multipart polygons were not selected when running this example.)