curvature versus slope
  n = 669005 
  X=0, Y = 29.75 +/- 17.53 
  Weighted least-squares fit:  Y = 27.0 + 1.313 X  + -0.00825 X**2 

slope versus dZ, curvature < 5
  n = 8922 

  Weighted least-squares fit:  Y = 2.9 + 0.045 X  + 0.00107 X**2 
     at X = 100, Y = 18.1 
     effective RMSE xy = 28.1 

slope versus dZ, curvature < 15
  n = 41964 

  Weighted least-squares fit:  Y = 3.3 + 0.013 X  + 0.00181 X**2 

curvature versus dZ, slope < 10
  n = 41270 
  X=0, Y = 3.08 +/- 1.71 
  Weighted least-squares fit:  Y = 2.7 + 0.167 X  + 0.00089 X**2 


Number of samples 670217
Max dz = 900
Mean dz = 10
RMS dz = 19.4422220952
100cm = 99.7951409767 percentile value of dz
Mean dz (curv<=5) = 4
RMS dz (curv<=5) = 7.0