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Slowtwitch Forums: Triathlon Forum:
frontal area calculation

mtboy

Nov 10, 09 11:11

Post #1 of 7 (231 views)

frontal area calculation	Can't Post

Dear friends:

I need a freeware to calculate frontal area from a front photo of a rider on the bike. Other method could be with a image software to merge frames.

The objective is optimize the aero position.

Can you help me?

Regards

Milton

WiScott

Nov 10, 09 11:52

Post #2 of 7 (215 views)

Re: frontal area calculation [mtboy] [In reply to]	Can't Post

Here's another "simpler" method: http://science.gcc.edu/..._Analysis_Report.pdf

-Scott

mtboy

Nov 10, 09 11:58

Post #3 of 7 (205 views)

Re: frontal area calculation [WiScott] [In reply to]	Can't Post

Thank you, I think the cutting procedure is very complicated for bike positioning. I search a photo editor to merge frames.

Other procedure is dartfish software.

Regards

Milton

Mito Chondria

Nov 10, 09 11:58

Post #4 of 7 (205 views)

Re: frontal area calculation [mtboy] [In reply to]	Can't Post

What are you trying to achieve? If you try to find the most aerodynamic setup based on frontal area I think you are wasting your time as aerodynamics is much more dynamic than static.

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jeremyb

Nov 10, 09 12:02

Post #5 of 7 (200 views)

Re: frontal area calculation [mtboy] [In reply to]	Can't Post

Depending on how often you want to do this, Photoshop has a trial period. Also, GIMP probably could do it----since Photoshop can.

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Laflore

Nov 10, 09 13:07

Post #6 of 7 (167 views)

Re: frontal area calculation [mtboy] [In reply to]	Can't Post

I don't know of any freeware. It would be straightforward to write a script that does simple bitmap thresholding (of luminance values) on a rider against a white backdrop, and then calculates the ratio of non-white versus white pixels. Assuming decent lighting, one could adjust the threshold to be quite accurate. Obviously, the more white the better and one could try tweaking aero positions to optimize this.

While aerodynamics is probably a lot more complicated than simple frontal area, it must be a big factor.

jkrabbe

Nov 10, 09 13:31

Post #7 of 7 (150 views)

Re: frontal area calculation [mtboy] [In reply to]	Can't Post

try a program called imageJ. It runs on java and is pretty simple, you calibrate the pixel count based on measuring something in the image and then just trace out the edge of the thing you want to measure the area of.