curvature versus slope
  n = 441078 
  X=0, Y = 41.37 +/- 24.65 
  Weighted least-squares fit:  Y = 55.1 + 1.882 X  + -0.01901 X**2 

slope versus dZ, curvature < 5
  n = 36060 

  Weighted least-squares fit:  Y = 0.2 + 0.916 X  + -0.00107 X**2 
     at X = 100, Y = 81.1 
     effective RMSE xy = 127.4 

slope versus dZ, curvature < 15
  n = 142551 

  Weighted least-squares fit:  Y = 2.1 + 0.872 X  + -0.00078 X**2 

curvature versus dZ, slope < 10
  n = 4136 
  X=0, Y = 9.94 +/- 8.37 
  Weighted least-squares fit:  Y = 10.8 + 0.963 X  + 0.10096 X**2 


Number of samples 447981
Max dz = 900
Mean dz = 53
RMS dz = 82.0853214649
100cm = 86.3909406872 percentile value of dz