Measuring Actual Distance

zivp

This might be a trivial question, but I'm a bit confused here.

Starting from this example: depth_preview, I'm trying to calculate the actual distance (in mm) to a specific point in my frame.

I have tried something like this:

while True:
inDepth = q.get() # blocking call, will wait until a new data has arrived
frame = inDepth.getFrame()
print(frame[250,250])

But the values I get back do not make much sense. What does 20 mean in this case??

What am I missing here? How do I calculate actual physical distance?

Thanks!

dhruvsheth-ai

check this example from Gen2 - https://github.com/luxonis/depthai-python/blob/develop/examples/29_3_object_tracker_video.py

erik

Hello @zivp,
so what you are viewing is disparity, not depth. You could set the stereo.setOutputDepth(True) and change code to send depth instead of disparity over xlink and then "decode" the depth frame on host + do some kind of thresholding + averaging to get a decent output. You should probably check spatial location calculator demo, which does it for you. You could decrease the size of ROI to get a depth in a certain "point" (small area). Hopefully, that demo can accomplish what you are looking for.