|
Different ways to measure/calculate frontal area (A)
This has come up in a few threads, decided to start a dedicated one.
The old trick was to photograph the car with a telephoto lens, cut the car out of the photo & weigh the cutout vs. the cutout + the rest of the photo. Using a known measurement on the car in the photo, area can be derived using the proportion of the photo's weight.
A more modern method is to take a digital photo, trace the car's outline & use a pixel-counting program to get the image vs. vehicle proportions.
The problem is, you need a very strong telephoto to make this work. 3x optical isn't enough (I already tried, and it was quite off, when comparing the known length of the front plate to the length of a wiper blade by counting pixels.)
I think a more accurate (but harder) way to do frontal area is to back the car up to a wall, then take a strong flashlight far away and point it at the car. Trace the outline of the shadow on the wall. Then photograph it and do the pixel counting.
EDIT: ideally you would use the sun at sunrise/set, but good luck finding such a wall/unobstructed sightline.
|