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| 2014-03-14 05:54:49 -0600 | commented question | Perspective Compensation when Measuring Distances on an Image with a known reference distance Thanks. This doesn't have to be 100% accurate so I may just ignore the radial distortion at the moment as the camera doesn't distort that much. Once I can find the correct calculations I shall take that into account to improve accuracy. |
| 2014-03-11 12:24:13 -0600 | asked a question | Perspective Compensation when Measuring Distances on an Image with a known reference distance I am trying to calculate the real world distance of an arbitrary line drawn along the field of view from a one point perspective, single camera setup. I will have a known distance running parallel. How can I find the compensation factor I need to apply to the pixel length of the measuring line?
Do I have to take into account the distance from the vanishing point, as the length per pixel increases the nearer you get to the vanishing point? Do I need to use the gradient of the known line to give me a rate of change? I have been reading up on cross ratios but I don't understand if they are applicable in this scenario as I seem to be measuring in the opposite direction in respect to the vanishing point to apply this. |
| 2014-01-16 06:22:01 -0600 | commented answer | Measurement within known diameter tube What units do you use for y and for height. Is height the image height in pixels? |
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| 2014-01-16 06:03:10 -0600 | commented answer | Measurement within known diameter tube wow thanks for your effort. |
| 2014-01-16 06:02:52 -0600 | received badge | ● Scholar (source) |
| 2014-01-16 05:48:57 -0600 | received badge | ● Student (source) |
| 2014-01-16 04:14:01 -0600 | commented question | Measurement within known diameter tube When reading up the only formulae that I can find you need to know real life object size to get the distance. |
| 2014-01-16 04:11:58 -0600 | commented question | Measurement within known diameter tube Recently bought a raspberry pi and was messing around trying to think of an application. Then I had a blockage in a drain pipe and wanted to know where it was. Nothing exciting really but is frustrating me now that I can't do it. |
| 2014-01-16 02:41:01 -0600 | commented question | Measurement within known diameter tube Principally I would like to know how to calculate the length of a line running parallel to the length of the tube but ideally any random straight line. |
| 2014-01-15 09:02:57 -0600 | commented question | Measurement within known diameter tube I would like to be able to draw a straight line and calculate the length of it in mm. Is this possible with the only known parameter being the diameter of the tube? |
| 2014-01-09 10:52:02 -0600 | received badge | ● Editor (source) |
| 2014-01-09 10:51:36 -0600 | asked a question | Measurement within known diameter tube Hi All, I am having trouble working out how to solve the following problem: I am acquiring images from a camera placed within a tube of known fixed diameter, I am trying to implement an interface whereby a user can draw a line between 2 points and the real world measurement should be calculated, this can be in any orientation they like. My first approach was to use trig, But then I thought this would be erroneous due to perspective distortion? Could anybody shed any light on this? Thanks, Digby Update Here is a screenshot. The mesh is moveable so I can select the vanishing point.
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