curvature versus slope
  n = 618642 
  X=0, Y = 50.58 +/- 23.02 
  Weighted least-squares fit:  Y = 60.6 + 1.896 X  + -0.02074 X**2 

slope versus dZ, curvature < 5
  n = 274075 

  Weighted least-squares fit:  Y = 12.2 + 0.305 X  + 0.00440 X**2 
     at X = 100, Y = 86.7 
     effective RMSE xy = 134.9 

slope versus dZ, curvature < 15
  n = 459655 

  Weighted least-squares fit:  Y = 12.0 + 0.369 X  + 0.00382 X**2 

curvature versus dZ, slope < 10
  n = 9062 
  X=0, Y = 16.38 +/- 8.37 
  Weighted least-squares fit:  Y = 16.8 + 0.385 X  + 0.02469 X**2 


Number of samples 622743
Max dz = 900
Mean dz = 45
RMS dz = 63.835726674
100cm = 92.2056129093 percentile value of dz