curvature versus slope
  n = 334815 
  X=0, Y = 7.16 +/- 3.77 
  Weighted least-squares fit:  Y = 4.9 + 3.847 X  + 0.00788 X**2 

slope versus dZ, curvature < 5
  n = 214431 
  X=0, Y = 15.47 +/- 8.33 
  Weighted least-squares fit:  Y = 13.2 + 0.325 X  + 0.00355 X**2 
     at X = 100, Y = 81.2 
     effective RMSE xy = 125.8 

slope versus dZ, curvature < 15
  n = 311406 
  X=0, Y = 16.66 +/- 8.92 
  Weighted least-squares fit:  Y = 12.1 + 0.652 X  + -0.00332 X**2 

curvature versus dZ, slope < 10
  n = 266997 
  X=0, Y = 14.55 +/- 7.07 
  Weighted least-squares fit:  Y = 14.2 + 0.799 X  + 0.26251 X**2 


Number of samples 335141
Max dz = 900
Mean dz = 14
RMS dz = 18.7882942281
100cm = 99.8946711981 percentile value of dz