curvature versus slope
  n = 653124 
  X=0, Y = 21.94 +/- 14.16 
  Weighted least-squares fit:  Y = 46.2 + 2.713 X  + -0.02842 X**2 

slope versus dZ, curvature < 5
  n = 46594 

  Weighted least-squares fit:  Y = 60.4 + 0.284 X  + -0.00157 X**2 
     at X = 100, Y = 73.2 
     effective RMSE xy = 64.8 

slope versus dZ, curvature < 15
  n = 151925 

  Weighted least-squares fit:  Y = 62.4 + 0.124 X  + 0.00064 X**2 

curvature versus dZ, slope < 10
  n = 14703 
  X=0, Y = 65.03 +/- 35.85 
  Weighted least-squares fit:  Y = 65.9 + -1.820 X  + 0.19052 X**2 


Number of samples 655741
Max dz = 900
Mean dz = 72
RMS dz = 100.319489632
100cm = 76.7966315969 percentile value of dz