Signal filtering to remove low frequency movement

I have the following signal - position of object against time.

I want to filter out the longer period signal (around 15 seconds) with a butterworth filter, so it basically removes the big surges? Hugely stuck!

Thanks

Answer 1

[Star Strider]

I would use a bandpass filter with an appropriate low-frequency cutoff to remove the baseline drift and d-c offset, and high-frequency cutoff to remove any high-frequency noise. Determine those frequencies by first doing a fft of your data. (The code between the first two plot images in the fft documentation is all you need to do for this.) My filter design procedure is here.