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Thread Subject:
finding diameter of pothole in the digital picture

Subject: finding diameter of pothole in the digital picture

From: nman2084

Date: 7 Jun, 2011 15:27:04

Message: 1 of 8

I just need some directions where i can start in finding diameter of pothole in digital picture. Do i need to have image processing toolbox of Matlab.
                                           naveen

Subject: finding diameter of pothole in the digital picture

From: ImageAnalyst

Date: 7 Jun, 2011 16:55:19

Message: 2 of 8

On Jun 7, 11:27 am, "nman2084 " <ng2...@yahoo.com> wrote:
> I just need some directions where i can start in finding diameter of pothole in digital picture. Do i need to have image processing toolbox of Matlab.
>                                            naveen

-----------------------------------------------------------------------
See my BlobsDemo image segmentation tutorial:
http://www.mathworks.com/matlabcentral/fileexchange/?term=authorid%3A31862
It uses coins which are pretty similar to potholes - basically finds
them and measures area, centroid location, perimeter, etc. You need
the Image Processing Toolbox.

Subject: finding diameter of pothole in the digital picture

From: nman2084

Date: 7 Jun, 2011 21:36:04

Message: 3 of 8

Thanks,
    I have few questions regarding the demo:

Equivalent Circular Diameter you calculate, what are the units? Is there a scale or something.

Also is there a way to get depth information, if i consider a pothole instead of coin?

Subject: finding diameter of pothole in the digital picture

From: ImageAnalyst

Date: 8 Jun, 2011 02:32:41

Message: 4 of 8

The units are in pixels. You'd have to know how many pixels are a
certain known size (like a meter or something) in order to get a
calibration factor that can give units in real-world units.

You can get depth info if you have a depth image, like you'd get from
a profilometer, or if you had some other way like a "stereo pair" or
"shape from shading" or something.

Prof. Bugao Xu at Univ Texas worked on a system that drove along
characterizing road conditions (potholes, alligator cracks etc.)
http://www.he.utexas.edu/txa/xures.php "Automated Pavement Surface
Distress Rating System for Asphaltic Pavements,"

Subject: finding diameter of pothole in the digital picture

From: nman2084

Date: 10 Jun, 2011 15:45:10

Message: 5 of 8

If i don't have depth image, is there a way to get z out for the pothole in the digital image using the pixels. Shape in this type of pothole is conical.

Subject: finding diameter of pothole in the digital picture

From: Steven_Lord

Date: 10 Jun, 2011 16:04:42

Message: 6 of 8



"nman2084 " <ng2084@yahoo.com> wrote in message
news:iste66$7u5$1@newscl01ah.mathworks.com...
> If i don't have depth image, is there a way to get z out for the pothole
> in the digital image using the pixels. Shape in this type of pothole is
> conical.

Certainly, as long as you have an algorithm that could distinguish, just
from the picture itself, whether this:

http://en.wikipedia.org/wiki/File:Tour_Eiffel_Wikimedia_Commons.jpg

is of the real Eiffel Tower or one of the smaller scaled-down replicas:

http://en.wikipedia.org/wiki/List_of_Eiffel_Tower_replicas

--
Steve Lord
slord@mathworks.com
To contact Technical Support use the Contact Us link on
http://www.mathworks.com

Subject: finding diameter of pothole in the digital picture

From: ImageAnalyst

Date: 10 Jun, 2011 16:41:56

Message: 7 of 8

On Jun 10, 11:45 am, "nman2084 " <ng2...@yahoo.com> wrote:
> If i don't have depth image, is there a way to get z out for the pothole in the digital image using the pixels. Shape in this type of pothole is conical.

------------------------------------------------------------------------------------------------------
I'm not an expert in getting 3D models from multiple camera views,
like these people:
http://www.canfieldsci.com/imaging_systems/face_and_body_systems/VECTRA_X3_Imaging_System.html

http://www.3dmd.com/
I'm sure the math is not trivial.

And I don't know much about "shape from shading," so you're on your
own there. I do know that you'd need multiple images where the angle
of the light changes and you look how the shadows move in the images.

Like Steve said, if you want real world units out, you're going to
have to do some kind of spatial calibration, otherwise everything is
in arbitrary pixel units.

Subject: finding diameter of pothole in the digital picture

From: nman2084

Date: 10 Jun, 2011 16:44:04

Message: 8 of 8

Has any one done a demo or something with finding z from the pixels. Any algorithms?
                   Thanks

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