## depth error

2ros0
Posts: 1
Joined: Tue Jul 16, 2019 3:00 pm

### depth error

Hi,

I was looking to see what kind of depth error I could expect using the stereo cameras here:https://nerian.com/support/resources/calculator/

On plugging in different values for "expected disparity error", I expected the depth error to vary linearly. But that doesn't seem to be the case.

I was using the formula

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``delta_Z = Z^2/(B*f) * delta_D``
where, delta_Z is depth error
Z is target depth
B is baseline
f is focal length
delta_D is expected disparity error

Is there something else in the nerian stereo cameras that I have to take into account?
k.schauwecker
Posts: 25
Joined: Mon Mar 25, 2019 1:12 pm

### Re: depth error

Hi,

your equation is wrong. Z is computed by:

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``````Z = B*f / D
``````
so a delta in D will result in:

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``````delta_Z(D) = B*f / (D + delta_D) - B*f/D
``````
this delta is dependent on the disparity (and hence the depth) and is thus not linear but it increases with the depth. The solution is approximately quadratic for small delta_D, which is what you see in the error chart.

Regards,
Konstantin