Question
Whats the best way to calculate sq. ft. of an area that is asymmetrical. The shape
had 9 sides.  

Answer
Make triangles and rectangles out of your assymetrical shape, then add their areas up.  

If you are looking to find VOLUME, keep reading:

The preferred method of volume for an odd area is called the End Area or Average End Area method, and it is like slicing a loaf (an odd-shaped loaf) of bread, then measuring each slice for areas of fills and voids ?take the average between the 搒lices? then add these averages all together.

This works really well for grading activities where there are both cut & fill portions and you want to 揵alance?the site so you don抰 have to import or export fill.  

It is an averaging method, so the results are only as fine as the thickness  of the 搒lices?you take, but if care is taken, can result in a pretty accurate measurement.  These measurements need to be perpendicular to each other, too.

In your case, it sounds like it is either one big hole or one big pile you what he number for.  Now, if it is a big pile, you can just get the area of the base, and the area of the top, then average the two (essentially only taking two 搒lices??top & bottom, and multiplying by the height, to get volume.

The equation is:
Volume = [(A1+A2)/2] x Length, where A1 and A2 are the actual end areas, and L is the distance between the areas.  The length can be either horizontal or vertical, but must be the same throughout (so no mixing horizontal & vertical measurements in the same equation)

For example, a pile of dirt is 200 square feet  at the base (measured by any means, and it doesn抰 have to be square)  and 10 square feet at the top, with an overall height of 15 feet.  
Our example: V=[(200+10)/2] x 15 =
210/2 = 105;  105 x 15 = 1,575 cubic feet of material
To get cubic yards, divide the cubic feet by 27, or a volume of 58.3 cubic yards.

For a 搈ulti-slice?example, you calculate EACH volume between the slices, then add all the average volumes together; The formula looks scary, it isn抰:
V= ([(A1+A2)/2] x L1)+( [(A2+A3)/2] x L2)+([(A3+A4)/2] x L)+(and so on卼o the last slice)

A spreadsheet really helps with these calculations.  Write back if you need additional help.  Sorry if it was TMI. ~Marc