curvature versus slope
  n = 912906 
  X=0, Y = 44.21 +/- 30.69 
  Weighted least-squares fit:  Y = 68.0 + 1.595 X  + -0.01565 X**2 

slope versus dZ, curvature < 5
  n = 69959 

  Weighted least-squares fit:  Y = 7.3 + 0.365 X  + -0.00146 X**2 
     at X = 100, Y = 29.3 
     effective RMSE xy = 44.5 

slope versus dZ, curvature < 15
  n = 285880 

  Weighted least-squares fit:  Y = 8.3 + 0.304 X  + -0.00013 X**2 

curvature versus dZ, slope < 10
  n = 41333 
  X=0, Y = 10.40 +/- 8.14 
  Weighted least-squares fit:  Y = 10.3 + 1.057 X  + 0.03350 X**2 


Number of samples 925906
Max dz = 900
Mean dz = 30
RMS dz = 44.3395985548
100cm = 96.5126049513 percentile value of dz
Mean dz (curv<=5) = 13
RMS dz (curv<=5) = 20.0997512422