curvature versus slope
  n = 2086817 
  X=0, Y = 24.51 +/- 16.97 
  Weighted least-squares fit:  Y = 22.0 + 1.138 X  + -0.00573 X**2 

slope versus dZ, curvature < 5
  n = 30664 

  Weighted least-squares fit:  Y = 3.7 + 0.067 X  + 0.00159 X**2 
     at X = 100, Y = 26.3 
     effective RMSE xy = 40.9 

slope versus dZ, curvature < 15
  n = 137774 
  X=0, Y = 4.47 +/- 2.91 
  Weighted least-squares fit:  Y = 3.8 + 0.064 X  + 0.00172 X**2 

curvature versus dZ, slope < 10
  n = 336135 
  X=0, Y = 4.29 +/- 2.66 
  Weighted least-squares fit:  Y = 4.1 + 0.148 X  + 0.00119 X**2 


Number of samples 2090002
Max dz = 900
Mean dz = 10
RMS dz = 19.7737199333
100cm = 99.8217705055 percentile value of dz
Mean dz (curv<=5) = 4
RMS dz (curv<=5) = 9.0