curvature versus slope
  n = 279925 
  X=0, Y = 55.27 +/- 40.35 
  Weighted least-squares fit:  Y = 79.0 + 0.596 X  + -0.00537 X**2 

slope versus dZ, curvature < 5
  n = 3057 

  Weighted least-squares fit:  Y = 7.0 + 0.464 X  + -0.00146 X**2 
     at X = 100, Y = 38.7 
     effective RMSE xy = 59.9 

slope versus dZ, curvature < 15
  n = 11892 

  Weighted least-squares fit:  Y = 7.2 + 0.598 X  + -0.00236 X**2 

curvature versus dZ, slope < 10
  n = 1035 
  X=0, Y = 7.38 +/- 5.47 
  Weighted least-squares fit:  Y = 8.5 + 0.544 X  + 0.04527 X**2 


Number of samples 282998
Max dz = 900
Mean dz = 58
RMS dz = 80.0
100cm = 82.3422780373 percentile value of dz