curvature versus slope
  n = 1760888 
  X=0, Y = 26.40 +/- 19.62 
  Weighted least-squares fit:  Y = 51.8 + 2.122 X  + -0.02318 X**2 

slope versus dZ, curvature < 5
  n = 83092 

  Weighted least-squares fit:  Y = 31.1 + 0.498 X  + -0.00099 X**2 
     at X = 100, Y = 71.1 
     effective RMSE xy = 100.4 

slope versus dZ, curvature < 15
  n = 191930 

  Weighted least-squares fit:  Y = 30.9 + 0.648 X  + -0.00123 X**2 

curvature versus dZ, slope < 10
  n = 43888 
  X=0, Y = 35.57 +/- 17.07 
  Weighted least-squares fit:  Y = 32.9 + 1.985 X  + -0.02755 X**2 


Number of samples 1767978
Max dz = 900
Mean dz = 78
RMS dz = 105.033328044
100cm = 70.3775725716 percentile value of dz
Mean dz (curv<=5) = 33
RMS dz (curv<=5) = 44.3621460256