Is Camera Calibration needed to get measurements from an image?

Question

I am working on an android application that measures distances (euclidean distances) from a digital image. I know that in order to get real world measures like cm or meters I have to use an object with a known dimensions. Is Camera Calibration needed to get measurements from an image if I am using an object as a reference?

Thanks.

What exactly are you trying to measure? Is it something on the reference object? Is it the reference object itself? — Zaphod, Jul 25 '13 at 11:17

score 2 · Answer 1 · edited May 23 '17 at 12:07

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Antonio Criminisi's PhD thesis contains all the basics on this issue. See this answer to a related question.

edited May 23 '17 at 12:07

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answered Jul 25 '13 at 19:14

Francesco Callari

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thanks :), I'm reading the paper that you recommend in that answer – xuandl Jul 29 '13 at 15:24
If the answer is helpful, please accept it - helps with reputation building. – Francesco Callari Jul 29 '13 at 17:03

score 1 · Accepted Answer · answered Oct 28 '13 at 11:27

Short: No

Long: Camera Calibration (parameters) are in terms of optimization an additional term (sometimes a polynom) which can improve the resulting accuracy.

Think about it as an regression: If you have enough data to fit an higher order polynomial with a better insample/outsample error then you should should use the additional parameter(s). If you don't have enough data then you overfit and the insample/outsample error will be worse.

Especially in photogrammetry camera calibration parameters need to have a certain angle and camera position or combinations of them (relative to the object which you measure). Otherwise you wont be able to calculate the parameter with an significant value.

Is Camera Calibration needed to get measurements from an image?

2 Answers2