curvature versus slope
  n = 485064 
  X=0, Y = 19.98 +/- 16.04 
  Weighted least-squares fit:  Y = 41.9 + 3.069 X  + -0.03528 X**2 

slope versus dZ, curvature < 5
  n = 94680 

  Weighted least-squares fit:  Y = 11.4 + 0.423 X  + 0.00204 X**2 
     at X = 100, Y = 74.1 
     effective RMSE xy = 115.0 

slope versus dZ, curvature < 15
  n = 182503 

  Weighted least-squares fit:  Y = 11.3 + 0.496 X  + 0.00156 X**2 

curvature versus dZ, slope < 10
  n = 66219 
  X=0, Y = 13.41 +/- 8.34 
  Weighted least-squares fit:  Y = 13.6 + 1.069 X  + 0.08885 X**2 


Number of samples 493219
Max dz = 900
Mean dz = 49
RMS dz = 83.8331676605
100cm = 85.7797449003 percentile value of dz