Find a sinusoid in a sensor data
Your plot above indicates position, I assume from a single reading (?).  Your goal is to measure motion, which involves multiple position measurements.  If you determine position on a regular interval, and then plot the position over time, your sinusoid should show up if it's significantly greater than the position uncertainty.

If, on the other hand, the above graph represents the reflections from multiple readings, you may be able to find the statistical distribution of a sinusoidal signal within it.