curvature versus slope
  n = 2370216 
  X=0, Y = 7.97 +/- 5.35 
  Weighted least-squares fit:  Y = 9.4 + 4.900 X  + -0.05605 X**2 

slope versus dZ, curvature < 5
  n = 1311015 
  X=0, Y = 11.43 +/- 6.31 
  Weighted least-squares fit:  Y = 6.0 + 0.284 X  + 0.00054 X**2 
     at X = 100, Y = 39.9 
     effective RMSE xy = 61.9 

slope versus dZ, curvature < 15
  n = 1917438 
  X=0, Y = 11.56 +/- 6.39 
  Weighted least-squares fit:  Y = 5.9 + 0.422 X  + -0.00074 X**2 

curvature versus dZ, slope < 10
  n = 1357195 
  X=0, Y = 7.68 +/- 5.27 
  Weighted least-squares fit:  Y = 6.6 + 1.374 X  + 0.13407 X**2 


Number of samples 2383775
Max dz = 900
Mean dz = 11
RMS dz = 20.8566536146
100cm = 99.3594613586 percentile value of dz