Hello all,
I am doing some tie line levelling. In order to create a smooth correction function to
apply to my data I use a combination of a binary spline and a low pass filter on my
intersection errors. My question is about the low pass filter. It seems that there is
a very definite limit on the useful length of it. I've uploaded an example to
http://www.datadonkey.com/filter.htm. In this case the line length is about 3000 fids
and the green dots (intersection errors) are about 50 fids apart. The purple line is
the result of the binary spline (settings of .76 and .9) The last grey line, which you
can barely see, is the filtered result of the purple line. In this example the low
pass cutoff is set at 500. I expected the data to get pretty much whacked at that
length. I've tried varying the length from 50 to 5000(!) and the results are always
the same. The difference is in the second decimal place.
Now, I'm not looking for filtering or levelling advice here. It just seems to me that
the cutoffs don't work the way I would expect on low pass filtering. Can anyone
comment?
Thanks
Marc Pelletier
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Data Donkey - Geophysical Data Processing, Consulting and Software Development
Creator of the POWER TOOLBOX utilities for OASIS montaj
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