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How to detect distance to say a blob or to an edge
Anonymous
16 year
How do i detect distance from the camera to say the line(edge detection) or to a blob if i go that route?
Is there any way to get those values using the roborealm software?
Im trying to build an autonomous vehicle, it needs the distance measurement to make logic decisions.
John Christian from Norway  [25 posts] 16 year
Do you mean the distance from the camera on the robot to the blob detected? The only way you can do that with a monoscopic camera is to know how big the blob is in real life and count the pixels of the blob. The amount of pixels in it can then be used to calculate an approximate distance (but with a fairly high error rate ofc). If the blob has lots of shadows and textures, making its separation difficult, using the pixel count might not be a good idea then. You could then use the blob bounding box for an approximate distance calculation. This will naturally only work for blobs that are fully in the camera. If the blob is clipped to either sides or top/bottom you will have to use either height or width of blob as an estimate (base this on which edge it touches).

If you have stereoscopic images you could calculate the distance between the matched blobs and use that as additional data for calculating distance (the further apart they are the closer the object is to the camera).
Anonymous 16 year
Thanks, im actually looking into using stereo cameras as the distance measurement is more precise, which is needed in this case. The only problem is that i dont think roborealm software supports stereo image processing(like distance aquisition) so i will use some other program.
Thanks for your help
John Christian from Norway  [25 posts] 16 year
RoboRealm does not have any stereo matching algorithm yet, but if you are able to separate the blob you are tracking from the rest of the image, then you should be able to do that on a stereo pair. RoboRealm does handle two camera inputs so its basically just to do the same detection on both images and get the COG for both and calculate the horizontal distance between these.
Anonymous 16 year
can you run the stereo image through a RGB filter to eliminate all the noise from the image then it will be possible to measure the distances better(having the blob say red) then measure the x axis distance then determine the distance form the camera.
thanks
Anonymous 16 year
You might find this related post interesting.

http://www.roborealm.com/forum/index.php?thread_id=710#1

STeven.
Anonymous 16 year
Thanks steven helped a lot, and im proberbly going to use the methodology stated there to aid my cause. Thanks

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