curvature versus slope
  n = 321922 
  X=0, Y = 37.56 +/- 25.04 
  Weighted least-squares fit:  Y = 61.2 + 1.529 X  + -0.01632 X**2 

slope versus dZ, curvature < 5
  n = 19778 

  Weighted least-squares fit:  Y = 5.7 + 0.665 X  + 0.00093 X**2 
     at X = 100, Y = 81.5 
     effective RMSE xy = 127.8 

slope versus dZ, curvature < 15
  n = 51625 

  Weighted least-squares fit:  Y = 6.2 + 0.703 X  + 0.00067 X**2 

curvature versus dZ, slope < 10
  n = 3787 
  X=0, Y = 10.55 +/- 6.44 
  Weighted least-squares fit:  Y = 7.7 + 3.753 X  + -0.00693 X**2 


Number of samples 325166
Max dz = 900
Mean dz = 74
RMS dz = 105.966975988
100cm = 74.2648370371 percentile value of dz