# Area density calculation

Discussion created by taihoon on Oct 8, 2010
Dear all,

I would like to know how my approach is right or wrong.
My goal is to get solve this equation in arcGIS;

S = S1 / S2
where, S: percentage area within the unit area / S1: area within the unit area / S2: unit area

input data is "polygon" layer which delineates area of interest (crime site, traffic accident site etc).

Here is what I did;

1. convert polygon to raster (cell size: 2 by 2)
2. make all values to 1 using raster calculator
3. make Nodata to 0 using CON and IsNull command
4. Focal sum (using rectangular, cell size: 8 by 8, and greater than the cell size 2 by 2m)
5. so value of result rater layer has the value range of 0 (no value of 1) to 64 (all unit areas - 64 cells - have value of 1)
6. add field of area then multiply by cell size, i.g., 4 m^2 (I multiplied this cell size to value (0-64) not to count because I want to get an area value in the unit area, not total area)
7. add field of density then calculate density ((area / (16 * 16) )*100)
8. convert raster to point based on density value
9. interpolate with this converted point layer
10. generate contour

That's it. please let me know which I forgot or other brilliant idea

one more question, if I use circle (radius 4 cells) in the step 4 instead of rectangular, what's the unit area of the circle? is it phi * 16^2 ?