curvature versus slope
  n = 523367 
  X=0, Y = 37.80 +/- 21.03 
  Weighted least-squares fit:  Y = 33.5 + 1.113 X  + -0.00664 X**2 

slope versus dZ, curvature < 5
  n = 3974 

  Weighted least-squares fit:  Y = 8.1 + -0.027 X  + 0.00166 X**2 
     at X = 100, Y = 21.9 
     effective RMSE xy = 32.1 

slope versus dZ, curvature < 15
  n = 19965 

  Weighted least-squares fit:  Y = 7.6 + 0.003 X  + 0.00151 X**2 

curvature versus dZ, slope < 10
  n = 14138 
  X=0, Y = 7.62 +/- 2.27 
  Weighted least-squares fit:  Y = 7.0 + 0.110 X  + 0.00053 X**2 


Number of samples 524661
Max dz = 900
Mean dz = 14
RMS dz = 26.83281573
100cm = 99.7135293075 percentile value of dz
Mean dz (curv<=5) = 8
RMS dz (curv<=5) = 11.0905365064