Chord Length

[BodkinArrow]

Hi all,

I intend to measure Chord Length and Arc Length in a gray scale image. Kindly advise.

[udka]

I am sorry without seeing proper image of what you are looking its difficult to advise first.

-And there are many measurements you can get in Particle measurements for binary image so you might need to convert gray scale to binary.

-You can check the list of measurements here: http://zone.ni.com/reference/en-XX/help/372916T-01/nivisionconcepts/particle_measurements/ and the VI here https://zone.ni.com/reference/en-XX/help/370281AA-01/imaqvision/imaq_particle_analysis/

[BodkinArrow]

Thank you for the measurements link.

This would be the image for which i intend to measure an arbitrary chord length. We may lose info in binary image as we will need to apply threshold hence particle analysis would not be first preference.

[udka · Accepted solution]

You need to find for inner circle or outer circle?

Math Part:

For Calculating Chord length you need to find radius and angle subtended at the center by the chord or perpendicular distance from the chord to the circle center: Once you have those parameters you can calculate the chord length by using formulas:

Source: http://www.mathopenref.com/chord.html

Similarly you can get for Arc length : http://www.mathopenref.com/arclength.html

Image Processing Part:

-I think you can get the radius of the inner or outer circle based on your requirement using IMAQ detect shapes.

https://zone.ni.com/reference/en-XX/help/370281M-01/imaqvision/imaq_detect_shapes/