curvature versus slope
  n = 30400 
  X=0, Y = 56.35 +/- 31.79 
  Weighted least-squares fit:  Y = 74.8 + 0.911 X  + -0.00875 X**2 

slope versus dZ, curvature < 5
  n = 622 

  Weighted least-squares fit:  Y = -0.2 + 0.524 X  + -0.00059 X**2 
     at X = 100, Y = 46.3 
     effective RMSE xy = 72.8 

slope versus dZ, curvature < 15
  n = 2281 

  Weighted least-squares fit:  Y = 1.6 + 0.576 X  + 0.00030 X**2 

curvature versus dZ, slope < 10
  n = 74 
  X=0, Y = 1.87 +/- 1.36 
  Weighted least-squares fit:  Y = -0.3 + 5.740 X  + -0.38155 X**2 


Number of samples 30705
Max dz = 900
Mean dz = 79
RMS dz = 137.640836963
100cm = 75.4632795962 percentile value of dz