Calculating the areas of polygon located inside a target polygon

[SawsanHadi]

I have two polygon shape files that represents the building footprints and the plot. I want to calculate the plot ratio (area of built/area of the plot). I used spatial join with sum function, but summing up the area of the polygons that located inside one plot is not calculted correctly. Any idea how to do that in arcmap?

[DanPatterson_Retired]

Do you have sample results?

An example showing the calculation versus the expected would help.

And both files are in the same projected coordinate system?

[SawsanHadi]

can you send me your email

[DanPatterson_Retired]

You can post here, the questions I asked don't require a separate email thread

[SawsanHadi]

the Plot_Ratio shows the calculated value with spatial join tool and the Actual_PL is the real values. 

[DanPatterson_Retired]

As per my initial post

• are the data in a projected coordinate system, or just the data frame?
• I don't see any area data and only 1 perimeter which seems to be in projected coordinates, 
• can you take 1 plot and show what the plot area is and the building footprint area is.

I suspect that your problems are with the coordinate system being geographic or in web mercator

[SawsanHadi]

My Data is the converted CAD file to shape file , then I defined the coordinate system for each shape file. None the less this might be true since I tried the same process with 3 different methods _summing up the building polygon per plot_. All are resulting incorrect result , see the Area_B that is calculated with spatial join are bigger than the plot area.for summing up the area. But using manual sum with filed calculator result  in a more realistic result.

[SawsanHadi]

The Projected Coordinate System  is WGS_1984_UTM_Zone_32N and the 
Projection is  Transverse_Mercator. So how to solve the problem? thank you for your reply!