curvature versus slope
  n = 491949 
  X=0, Y = 27.16 +/- 19.84 
  Weighted least-squares fit:  Y = 46.8 + 2.423 X  + -0.02569 X**2 

slope versus dZ, curvature < 5
  n = 33007 

  Weighted least-squares fit:  Y = 63.4 + -0.030 X  + 0.00285 X**2 
     at X = 100, Y = 89.0 
     effective RMSE xy = 98.0 

slope versus dZ, curvature < 15
  n = 100954 

  Weighted least-squares fit:  Y = 61.7 + -0.073 X  + 0.00357 X**2 

curvature versus dZ, slope < 10
  n = 15072 
  X=0, Y = 66.78 +/- 22.31 
  Weighted least-squares fit:  Y = 61.0 + 0.839 X  + -0.00387 X**2 


Number of samples 495941
Max dz = 900
Mean dz = 79
RMS dz = 109.183332061
100cm = 75.1010704902 percentile value of dz