The Dissolve tool in ArcGIS Pro and ArcMap creates a larger acre area compared to the input feature layer.

参考情報

対処法

There are two ways to calculate the area in acres in the Clip output to compare it to the calculated area in the Dissolve output.

Workflow 1:

1. Run the Clip tool.

2. Add a field to the Clip output (Clip_Acres) and calculate the area in acres using the CalculateGeometry tool.

3. Open the clip output table, right-click the Clip output (Clip_acres) field, and select Statistics. The Statistics window is open. Note the 'Sum' Statistic.

4. Run the Dissolve tool on the Clip output and select the desired field (Soilburn_Sev) as the Dissolve field.

5. Add a field to the Dissolve output (Dissolve_Acres) and calculate the area in acres using the CalculateGeometry tool.

6. Open the Dissolve output table, right-click the Dissolve output (Dissolve_Acres) field, and select Statistics. The Statistics window is open. Note the 'Sum' Statistic.

There may still appear to be a significant difference, it is well within the tolerance of the input data during processing. Run the SymmetricalDifference tool on the Clip and Dissolve output to check. If the data is within the tolerance of the input, the SymDiff output should be empty.

Workflow 2:

Use the Layer Split policy on the GIS_Acres field and then run the Clip tool so when the field is inserted into the Clip output the values represent the ratio of each input feature clipped and then included in the Clip output. Refer to https://pro.arcgis.com/en/pro-app/latest/tool-reference/data-management/make-feature-layer.htm. 

The important part from the doc:

"A split policy can be set by using the Field Info control's Ratio option. The split policy comes into effect any time the feature layer is being used as an input to a tool and a geometry of the input feature layer is split during processing. When the split geometry is sent to the output, a ratio of the input attribute value is calculated for the output attribute value. When Ratio is enabled, whenever a feature in an overlay operation is split, the attributes of the resulting features are a ratio of the attribute value of the input feature. The output value is based on the ratio in which the input feature geometry was divided. For example, if the input geometry was divided equally, each new feature's attribute value is assigned one-half of the value of the input feature's attribute value. The Ratio policy only applies to numeric field types.

The default is none (unchecked). This means the attribute of the two resulting features takes on a copy of the original object's attribute value."

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