Calcular a área percentual de um mapa de declividade classificado no ArcGIS Pro

Resumo

A slope map provides a visual representation of the slope's steepness in light to dark color gradients. For analysis, a slope map is classified into areas based on the degree of steepness. This article provides the workflow to calculate the percentage area of a classified slope map in ArcGIS Pro.

Procedimento

1. Reclassify the slope map based on the desired range of steepness.
   1. On the ArcGIS Pro top ribbon, click the Analysis tab, and click Tools.
   2. In the Geoprocessing pane, search for and click Reclassify (Spatial Analyst Tools). The Reclassify window opens.
   3. For Input raster, select the slope raster. In this example, the slope raster is Slope_map_1.
   4. Under Reclassification, click Classify. The Equal Interval Classification pop-up displays. In the Equal Interval Classification pop-up, specify Number of classes, and click OK. In this example, the specified number is 4.
   5. Alternatively, manually specify the values in the Reclassification table.

6. For Output raster, specify a name for the output in the desired folder location.
7. Click Run.

2. Convert the reclassified slope raster to polygon.
   1. In the Geoprocessing pane, search for and click Raster to Polygon (Conversion Tools). The Raster to Polygon window opens.
   2. For Input raster, select the reclassified raster. In this example, the raster is Reclass_Slop1.
   3. For Output polygon features, specify a name for the output. In this example, the output name is Raster_to_Polygon.
   4. Check the Create multipart features check box.
   5. Leave other parameters at default.
   6. Click Run.

3. Add a new field in the attribute table of the polygon output.
   1. Open the attribute table of the polygon layer.
   2. In the attribute table, click Add Field . The Fields view opens.
   3. In the Fields view, specify a name for the new field in the Field Name column. In this example, the new field is Percentage_area.
   4. Double-click the Alias column of the new field, and specify an alias for it. In this example, the alias is Percentage_area.
   5. Click the Data Type column of the new field, and select Double from the drop-down menu.
   6. On the top ribbon, on the Fields tab, click Save .

4. Calculate the total area of the slope map.
   1. In the attribute table of the polygon layer, right-click the Shape_Area field, and click Summarize. The Summary Statistics window opens.
   2. For Input Table, select the polygon layer. In this example the polygon layer is Raster_to_Polygon.
   3. For Output Table, specify a name for the output in the desired folder location.
   4. In the Statistics Field(s) section, click the drop-down box under Field, and select Shape_Area.
   5. For Statistic Type, ensure Sum is selected.
   6. Click Run.

7. Open the output table, and copy the SUM_Shape_Area value.

5. Calculate the percentage area of each classified area of the slope map.
   1. Open the attribute table of the polygon layer. Right-click the new field created in Step 3, and click Calculate Field. The Calculate Field window opens.
   2. For Input Table, select the polygon layer. In this example, the polygon layer is Raster_to_Polygon.
   3. For Field Name (Existing or New), select the new field created in Step 3. In this example, the field is Percentage_area.
   4. For Expression Type, ensure Python 3 is selected.
   5. In the Expression section, double-click Shape_Area under Fields. Click the multiplication (*) symbol. In the expression box, type 100. Click the division (/) symbol. In the expression box, paste the SUM_Shape_Area value copied in Step 4. The following expression is populated in the Percentage_area expression box:

!Shape_Area! * 100 / 129858493.81171

6. Click Run.

The following image shows the attribute table containing the percentage area of the classified slope map.