A common task I have is to take a site area that encompasses several different properties and make a map showing how much of each property is within the site boundary. Then I calculate the proportion of each property compared to the site area. The properties are all single part polygons in a feature (white lines) and the site area is a single polygon (red line).
I made a ModelBuilder tool to automate this, but I can't figure out a good way to automatically calculate the total site area and then use that number in the field calculator to calculate the property proportion for each property.
The model uses the intersect tool to create a feature clipping each property to the site boundary and calculates the area of each property within the site boundary. This is where I need help. Currently, I have a model parameter to manually input the total site area. ModelBuilder uses this value to calculate the property proportion for each property with the equation below.
To lower risk of mistakes, I want to automatically sum the property areas calculated from the intersect tool and use that number as the total site area to calculate property proportion. This way I know that the property proportions will add up to 100% and I don't have to calculate the total site area myself to input manually.
I'm using ArcMap 10.8 and am not familiar with Pyhton (unfortunately).