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Old 01-04-2010, 06:29 PM   #1 (permalink)
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Frontal Area by photographic method

Some members are having a time arriving at an accurate frontal area for their vehicle.
Here's an obtuse method from the Motor Industry Research Institute (MIRA) in the UK.
It requires a laboratory grade scale.
Here's the nuts and bolts of it ( and I apologize if it's already been mentioned elsewhere).
A telephoto image of the vehicle is taken with a very "long" lense on the camera and from great distance.The photo can be taken from ahead or behind the vehicle."Frontal" area of a vehicle is really erroneous and has nothing to do with the front of anything.
It would be the area of the shadow of the vehicle cast by sunlight or laser light from front or rear,cast onto a perpendicular surface.
When the photo is taken,a plate,1-foot-by-1-foot,or 1 meter-square is mounted on the vehicle any place convenient,as long as it is also perpendicular to the camera.
The image is enlarged and printed at a convenient scale.
The image of the vehicle is cut away from the surrounding part of the photo and weighed on the scale to get the total "area" weight.
Afterwards,the "square-foot" or "square-meter" is cut away from the vehicle image and weighed by itself to establish it's respective "weight."
By comparing the "weight" of the vehicle to the reference weight,you can establish the frontal area.
This is basically how "Pi" was determined(using the weight a uniform wall-section metal sphere).
You need a very accurate scale.

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Old 01-04-2010, 09:03 PM   #2 (permalink)
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Hi Phil,

A refinement of this method is to insert the photo into a CAD program, and scale its size accurately (by measuring a known distance in the photo), and then trace the outline of the car with a polyline. This has to be done manually, but it not all that hard, and it is pretty accurate. Then the CAD program can simply tell you the area. (It can also tell you things like the perimeter length.)

I think that the photo is the hardest to get right -- I think that there are photo editors that can correct the photo for perspective distortion; if the camera is digital and a known brand and model, if the lens is a standard model. Barrel distortion and other types of geometric distortions can be corrected for in a decent quality dSLR camera.
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Old 01-05-2010, 04:03 AM   #3 (permalink)
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hmm, this sounds interesting.


would tenths of a gram be sensitive enough?
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Old 01-05-2010, 12:14 PM   #4 (permalink)
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Hello -

This is from the Car Styling magazine :





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Old 01-05-2010, 01:27 PM   #5 (permalink)
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Cad

Quote:
Originally Posted by NeilBlanchard View Post
Hi Phil,

A refinement of this method is to insert the photo into a CAD program, and scale its size accurately (by measuring a known distance in the photo), and then trace the outline of the car with a polyline. This has to be done manually, but it not all that hard, and it is pretty accurate. Then the CAD program can simply tell you the area. (It can also tell you things like the perimeter length.)

I think that the photo is the hardest to get right -- I think that there are photo editors that can correct the photo for perspective distortion; if the camera is digital and a known brand and model, if the lens is a standard model. Barrel distortion and other types of geometric distortions can be corrected for in a decent quality dSLR camera.
A troglodite as myself should have been aware that today's software would not see calculating a described area as a challenge.
I'm doing a huge form of Darin's self-administered head-slap!
And I now vaguely remember that Darin "calculated" frontal areas like this before at the forum.Duh!!!!!!!!!!!!
Isn't senility wonderful!
Thanks!

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