Surface metrology open profile spline filter
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Author:  ALdavis [ Wed Jun 03, 2020 7:03 pm ]
Post subject:  Surface metrology open profile spline filter

Hello everyone, I am developing a demo to detect the ripples generated on railway tracks, I would appreciate any help or indication to use this library properly, thanks in advance.

After scanning and obtaining values ‚Äč‚Äčevery 1mm, it is necessary to filter long wave undulations (generated every 1000mm) to center the signal to the axis. I think the roughness analysis like ISO 16610 can be adapted correctly to my needs. You can take the following example image, where I apply a Spline (like or Gaussian filter (like with a 1000mm cut-off and I get the red line, which I can use to center the signal on the axis (subtracting this line from the original signal).

I am more focused on the splines and I don't know if the way to operate would be to make multiple splines (every 1m) and then join them, or if the spline function offers a value (windows or cut-off) for what I have described. Also, there are a lot of spline functions and I don't know which is the one indicated for the desired, supposedly cardinal cubic splines.

Please help me, I just came to this forum. I just need that red line to center the signal and to be able to measure wave amplitudes, like distances between peaks.

I would also appreciate if you indicated me to filter outliers.

spline cut-off 1m.jpg
spline cut-off 1m.jpg [ 891.49 KiB | Viewed 683 times ]

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