Bike Ride Spectrogram

This is a spectrogram of the accelerometer data collected on my smartphone as I ride my bike.  The y-axis is the time (it was about a 909 second -- 15m 9s -- ride) and goes from top to bottom.  The x-axis is the frequency (0 to about 100Hz) and goes from left to right.  Lots of interesting harmonics and other complex structures.  This is sampling every 100 measurements, or at about 2 Hz (once every 0.5 seconds):

The plot above is also the sum of the x, y, and z axes.  Here are the individual axes:

X:

Y:

Z:

Here's a plot of the z amplitudes (in g's) versus time (x-axis, seconds).  This is sampling about every 0.5 seconds.

Here's the same data, but just every data point with no skipping:

Here's another ride earlier that day, going the opposite way.  This is the x-axis g-force on the smartphone accelerometer: