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Measuring circumference and height of trees and tall cacti, and size of tree canopy
To measure the circumference of trees and tall cacti
Use a tape measure and wrap around the trunk of the tree. Measure at the same height for each tree/cacti. Typically this height is about 1.35m from the ground (if your students are short, than use a lower height, but make sure it is the same for all measurements)
To estimate the height of trees and tall cacti
 Method 1: Attach a plumbline at right angles to an isosceles triangle made of cardboard. (DIAGRAM)
Move until you can sight the top of the tree along the sloping edge of the triangle. Keep the upright edge vertical using plumbline. Measure the distance from the tree. Add your eye height to give you the treeÍs height.
Method 2: Measure your shadow. Measure the tree's shadow (make your shadow measurement during the same time of day). Calculate the tree's height using the following:
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Height of tree
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Your height
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Tree's shadow
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Your shadow
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Alternatively, you can place a meter stick upright and measure it's shadow in place of measuring the student's shadow.
To estimate the size of the tree canopy:
Method 1: Measure the perimeter of the canopy and use geometry to calculate area.
Method 2: Measure the diameter of the canopy, assume it is a circle and calculate the area.
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