Measurement accuracy of D415 and linear dependency
Hello again, I wanted to ask, what is the measurement accuracy of D415 camera? Intel says that it's 1% depending on height of camera. Is that mean accuracy will be ±2 mm from a 2 metre distance? And is there a correlation between accuracy and camera's height? I mean, can we somehow subtract or add error to measurement result? I hope I explained my question properly 😅
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Hi Baltabai K It is less than 1% of the distance from the camera. At 1 meter range, this translates to an accuracy of between 2.5mm and 5mm. Error increases linearly over distance (a phenomenon called RMS Error), meaning that the amount of error in depth measurement scales up as an observed object becomes further away from the camera.
There are ways in which accuracy can be improved, such as using the optimal depth resolution for that camera model (which is 1280x720 on the D415) or applying the High Accuracy visual preset configuration to shift the balance of the camera's configuration priorities in favor of accuracy whilst sacrificing some fill rate (the Medium Density preset provides a balance between accuracy and fill rate).
https://dev.intelrealsense.com/docs/d400-series-visual-presets
In regard to height: if the camera is pointing downwards towards the ground from a height then the same error over distance measurement rules should apply as when the camera is facing forwards.
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Thank you, MartyG for quick reply!
Yes, camera facing downwards and we are using 1280x720 on D415 and 840x480 on D435. We are making our own app using realsense library on python. Would you mind tell us what configurations are used in High Accuracy preset? Does camera has constant RMS error value, D415 in particular? We would like to increase accuracy to 1 - 1.5 mm if it even possible.
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The preset file HighResHighAccuracyPreset.json would be an appropriate choice, as it covers both 848x480 and 1280x720 under the definition of 'High Resolution'. If you click on the link below then you can see the configuration details that are applied by that High Accuracy preset.
RMS is governed by a maths formula, so in theory it should always behave the same. In practice though, there are a range of factors, such as environmental conditions and lighting, that may influence the amount of noise in an image.
If you would like to learn more about RMS Error and the maths formula for it, the section of Intel's excellent camera tuning guide forthe 400 Series cameras that is linked to below should be helpful.
It may be difficult to achieve the range of accuracy that you are seeking at a 2 meter range. Having a well-calibrated camera and applying Advanced Mode functions to increase the confidence of depth values may help though.
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RMS Error starts at around 0 at the camera lens and scales over distance. So at 70 cm range you should stand a chance of achieving improved accuracy.
If changing the D435 for the new D455 model is an option for you, the D455 has 2x improved depth measuring accuracy over distance than the D435. So for example, at 6 meters range it has the same accuracy as the D435 does at 3 meters.
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