curvature versus slope
  n = 9982262 
  X=0, Y = 6.98 +/- 3.30 
  Weighted least-squares fit:  Y = 9.2 + 5.250 X  + -0.06203 X**2 

slope versus dZ, curvature < 5
  n = 3530385 

  Weighted least-squares fit:  Y = 7.6 + 0.426 X  + -0.00247 X**2 
     at X = 100, Y = 25.6 
     effective RMSE xy = 38.3 

slope versus dZ, curvature < 15
  n = 6288782 

  Weighted least-squares fit:  Y = 8.2 + 0.455 X  + -0.00160 X**2 

curvature versus dZ, slope < 10
  n = 4345002 
  X=0, Y = 9.00 +/- 5.91 
  Weighted least-squares fit:  Y = 9.1 + 1.504 X  + 0.02893 X**2 


Number of samples 10252173
Max dz = 800
Mean dz = 21
RMS dz = 36.0970912956
100cm = 96.9965976969 percentile value of dz