curvature versus slope
  n = 693999 
  X=0, Y = 49.06 +/- 31.74 
  Weighted least-squares fit:  Y = 63.5 + 1.849 X  + -0.01866 X**2 

slope versus dZ, curvature < 5
  n = 94462 

  Weighted least-squares fit:  Y = 13.1 + 0.055 X  + -0.00032 X**2 
     at X = 100, Y = 15.4 
     effective RMSE xy = 12.7 

slope versus dZ, curvature < 15
  n = 257800 

  Weighted least-squares fit:  Y = 12.9 + 0.099 X  + 0.00058 X**2 

curvature versus dZ, slope < 10
  n = 17927 
  X=0, Y = 13.54 +/- 10.64 
  Weighted least-squares fit:  Y = 15.5 + 0.555 X  + -0.03735 X**2 


Number of samples 704762
Max dz = 900
Mean dz = 29
RMS dz = 50.8527285404
100cm = 95.3486425205 percentile value of dz
Mean dz (curv<=5) = 11
RMS dz (curv<=5) = 16.3095064303