# Thneed Weekly – Week 2014 – 32

EUREKA!!!!

Thneed Weekly returns.  Back in week 2014 – 28 of Thneed Weekly we covered briefly what a D-Tape was and how the units were multiplied out to be PI units to automatically provide the user with the diameter.  This week we will derive the formula to calculate basal area of a tree.  Basal area is a metric that foresters use to determine stocking of an area among other things.  All foresters that use English units have had burned in to there brain:

But what the heck is that.  The Math penguin that usually hides in a dark office will try to shed some light on this and provide it in both English and Metric units.  Should be a good time figuring that out.

## The Assumptions:

 English Metric Diameter Inches Diameter Centimeters 12 inches per foot 100 centimeters per meter BA = Square Feet BA = Square Meters π = 3.1415926535

## The Problem:

You have measured a tree with a D-Tape that is 13″ (~33cm) in Diameter Breast Height.  What is the basal area of this tree?