curvature versus slope
  n = 1535155 
  X=0, Y = 37.31 +/- 23.07 
  Weighted least-squares fit:  Y = 54.1 + 2.337 X  + -0.02472 X**2 

slope versus dZ, curvature < 5
  n = 83881 

  Weighted least-squares fit:  Y = 11.2 + 0.337 X  + -0.00030 X**2 
     at X = 100, Y = 41.9 
     effective RMSE xy = 63.5 

slope versus dZ, curvature < 15
  n = 441760 

  Weighted least-squares fit:  Y = 10.7 + 0.351 X  + -0.00008 X**2 

curvature versus dZ, slope < 10
  n = 8167 
  X=0, Y = 16.46 +/- 8.46 
  Weighted least-squares fit:  Y = 15.3 + -0.604 X  + 0.17010 X**2 


Number of samples 1557143
Max dz = 900
Mean dz = 36
RMS dz = 56.3471383479
100cm = 94.0566794443 percentile value of dz