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# Calculating Effective Projected Area (EPA)

## Calculating Effective Projected Area (EPA)

(OP)

To calculate the Effective Projected Area (EPA) for situations like outdoor lighting (involving fixtures and poles) it's a function of both the projected area AND the drag coefficient. Check out this literature from GE:

https://secure.ge-lightingsystems.com/gels01/r2/productcentral/htmls/literature.html

Click on "Poles/Brackets," and on the 3rd page of the pdf it says what I said.

One little difference between using the drag coefficient or not is that the orientation of the pole might differ in calculating the EPA. For example, if you look at a square pole, it has a higher projected area if you look at it like a diamond and say PA = height x width x 1.414. But a diamond has lower wind resistance than a square, so the maximum EPA might come from other orientation where you have PA = height x width.

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