curvature versus slope
  n = 3262552 
  X=0, Y = 20.66 +/- 15.64 
  Weighted least-squares fit:  Y = 22.5 + 1.481 X  + -0.01047 X**2 

slope versus dZ, curvature < 5
  n = 114506 
  X=0, Y = 3.61 +/- 2.38 
  Weighted least-squares fit:  Y = 4.3 + 0.083 X  + 0.00096 X**2 
     at X = 100, Y = 22.2 
     effective RMSE xy = 34.2 

slope versus dZ, curvature < 15
  n = 431000 
  X=0, Y = 3.79 +/- 2.44 
  Weighted least-squares fit:  Y = 4.5 + 0.071 X  + 0.00125 X**2 

curvature versus dZ, slope < 10
  n = 422021 
  X=0, Y = 4.63 +/- 2.97 
  Weighted least-squares fit:  Y = 4.6 + 0.110 X  + 0.00179 X**2 


Number of samples 3266056
Max dz = 900
Mean dz = 11
RMS dz = 17.7200451467
100cm = 99.8660463874 percentile value of dz
Mean dz (curv<=5) = 5
RMS dz (curv<=5) = 6.40312423743