How to Calculate Frontal Area
Calculating frontal area can be of interest when, for example, determining the profile of a vehicle. Contour matters for wind resistance, but so does frontal area. There are several possible ways of calculating frontal area, from taking a photo using a telephoto lens to using a laser level to using a pixel-counting program. High school geometry can determine the area.
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Things You'll Need
- Tape measure
- Laser measure
- Light source
- Large wall
- Pencil, pen or marker
Instructions
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By Geometry
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1
Park the vehicle perpendicular to the wall at night.
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2
Place a light source far from the front of the vehicle, on the ground.
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3
Use a measuring laser to measure the perpendicular distance from the light to the wall.
Break up the measurements to do this accurately. Measure from the light to the front of the vehicle. Then measure from the front of the vehicle to the wall.
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4
Measure the height and width of the shadow Locate the corresponding part of the vehicle casting the precise point of shadow where you measured. Measure the corresponding vehicle width and height at these points.
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5
Fully trace the outline of the shadow with a pencil, pen or marker.
If the wall is light-colored, the shape can be traced out directly onto the wall. If the wall needs to be protected from tracing marks, then poster board or roll paper can be affixed to the wall with staples or duct tape.
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6
Back out the vehicle and wait until daylight.
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7
Draw blocks of equal size to fill the shadow outline.
Make the size small enough to meet your accuracy needs.
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8
Count the blocks.
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9
Find the ratio of distance from light to car and the distance from light to wall. Calculate the ratio of car width and height to shadow width and height. These ratios should be the same. If not, you may want to reproduce some steps above to trace the discrepancy. The reason the ratios should be the same is because a triangle of light rays from the light to the front of the car is similar to the triangle from the light to the shadow.
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10
Multiply the average of the above ratios by the number of blocks. This will give you the frontal area.
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