# How can I calibrate a fixed camera to obtain accurate measurements of objects at different distances, despite height variations and pixel distortion?

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arezki on 19 Jul 2024 at 9:31
Commented: Walter Roberson on 23 Jul 2024 at 22:46
I have a problem with calibration for detecting objects at different distances. I have a fixed camera, but the objects are not stationary. The issue is that when I perform the calibration using a scale to detect objects with real measurements, if the height changes, I get different results due to pixel variation. My question is how can I calculate the measurements of any object at varying distances to obtain accurate real-world results?"
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Umar on 22 Jul 2024 at 18:59
No problem, @arezki, glad to help out and we are still here to assist you further if you have other questions or concerns.
arezki on 23 Jul 2024 at 8:34
I conducted these tests on the two stones because I wanted to integrate the results to create a scale for determining the size of any stone relative to the distance. The distance is a variable, as you can see, but the actual size of the object does not change even if the height increases. is there a method to create a scale or derive an equation for determining the size of any stone relative to the distance? The distance is a variable, as you can see, but the actual size of the object does not change even if the height increases.?

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### Accepted Answer

Matt J on 22 Jul 2024 at 10:35
You cannot determine the size of the object from a single camera without knowing its distance from the camera. You would need two cameras for that, and you would need to perform stereo camera calibration of that system, see,
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Matt J on 23 Jul 2024 at 20:21
Edited: Matt J on 23 Jul 2024 at 21:01
Correct. That was my original answer, and it is still my answer. What you are trying to do cannot be done with one camera.
Walter Roberson on 23 Jul 2024 at 22:46
Exception:
If the focal length of the camera is fixed and is suitably arranged, then you might possibly be able to do texture matching to detect how out of focus objects are, and use that information to estimate distance.

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