To calculate the area, perimeter, or length of different features in a map, it is essential to consider the geometry of each layer. The layer must have a defined coordinate system, as calculations cannot be performed without it.
When working with shapefiles, or if there are changes to the geometry of a layer, the fields for area, perimeter, or length are not automatically updated. Therefore, it is necessary to recalculate these values after any modification.
To begin, the user should right-click on the corresponding layer and open the “Attribute Table”. New numeric fields must be created for each geometric parameter to be calculated (such as area, perimeter, or length).
After creating the necessary fields, right-click on the header of one of these fields (e.g., “Area”) and select “Calculate Geometry”. Within the “Geometry Attributes” section, choose the desired geometric property—such as “Area”—and define the appropriate units (e.g., hectares). It is also necessary to confirm or select the coordinate system that will be used.
In some cases, the user must define the “Output Coordinates” under the “Environments” tab, especially when working with custom projections or unit conversions.
This method must be repeated to calculate all areas in hectares for each polygon layer, such as “lake” and “plant_cover”.
Calculation of geometries in ArcGIS Pro.
To calculate the perimeter of a polygon layer, for example “lake”, the same steps are followed. The only difference is the selection of “Perimeter” instead of “Area” under the “Geometry Attributes” section. The perimeter is typically measured in meters.
In the case of polyline layers, such as “road_network” and “water_network”, only the length can be calculated. This length may be expressed in various units such as meters, kilometers, or feet, depending on the needs of the analysis.
For point layers, only the XY coordinates can be calculated. These coordinates represent the location of each point in space and are useful for positioning and spatial analysis.
The “Calculate Geometry” tool enables users to compute geometrical values based on the specific type of each layer, making it a fundamental function for spatial data analysis in ArcGIS Pro.