curvature versus slope
  n = 504350 
  X=0, Y = 48.12 +/- 27.17 
  Weighted least-squares fit:  Y = 63.5 + 1.703 X  + -0.01827 X**2 

slope versus dZ, curvature < 5
  n = 37105 

  Weighted least-squares fit:  Y = 22.4 + 0.050 X  + 0.00409 X**2 
     at X = 100, Y = 68.3 
     effective RMSE xy = 101.3 

slope versus dZ, curvature < 15
  n = 147001 

  Weighted least-squares fit:  Y = 20.8 + 0.132 X  + 0.00380 X**2 

curvature versus dZ, slope < 10
  n = 1695 
  X=0, Y = 28.09 +/- 13.77 
  Weighted least-squares fit:  Y = 29.6 + -2.988 X  + 0.48290 X**2 


Number of samples 515814
Max dz = 900
Mean dz = 62
RMS dz = 92.822411087
100cm = 81.7102676546 percentile value of dz