curvature versus slope
  n = 1846868 
  X=0, Y = 28.71 +/- 20.29 
  Weighted least-squares fit:  Y = 47.1 + 2.374 X  + -0.02365 X**2 

slope versus dZ, curvature < 5
  n = 79532 

  Weighted least-squares fit:  Y = 7.5 + 0.236 X  + -0.00093 X**2 
     at X = 100, Y = 21.8 
     effective RMSE xy = 32.1 

slope versus dZ, curvature < 15
  n = 391673 

  Weighted least-squares fit:  Y = 9.4 + 0.166 X  + 0.00051 X**2 

curvature versus dZ, slope < 10
  n = 23933 
  X=0, Y = 8.90 +/- 5.74 
  Weighted least-squares fit:  Y = 7.6 + 2.030 X  + -0.06848 X**2 


Number of samples 1872663
Max dz = 700
Mean dz = 30
RMS dz = 52.4690384894
100cm = 95.3532482887 percentile value of dz