curvature versus slope
  n = 4147317 
  X=0, Y = 20.53 +/- 14.66 
  Weighted least-squares fit:  Y = 14.2 + 1.492 X  + -0.00832 X**2 

slope versus dZ, curvature < 5
  n = 45578 

  Weighted least-squares fit:  Y = 3.4 + 0.108 X  + 0.00048 X**2 
     at X = 100, Y = 19.0 
     effective RMSE xy = 29.3 

slope versus dZ, curvature < 15
  n = 252412 
  X=0, Y = 3.42 +/- 2.06 
  Weighted least-squares fit:  Y = 4.0 + 0.058 X  + 0.00144 X**2 

curvature versus dZ, slope < 10
  n = 1024761 
  X=0, Y = 4.22 +/- 2.41 
  Weighted least-squares fit:  Y = 4.4 + 0.087 X  + 0.00198 X**2 


Number of samples 4151803
Max dz = 900
Mean dz = 9
RMS dz = 17.9164728672
100cm = 99.8732839684 percentile value of dz
Mean dz (curv<=5) = 4
RMS dz (curv<=5) = 5.74456264654