curvature versus slope
  n = 859054 
  X=0, Y = 62.02 +/- 25.21 
  Weighted least-squares fit:  Y = 72.6 + 1.501 X  + -0.01655 X**2 

slope versus dZ, curvature < 5
  n = 317523 

  Weighted least-squares fit:  Y = 44.6 + 0.240 X  + -0.00038 X**2 
     at X = 100, Y = 64.8 
     effective RMSE xy = 73.9 

slope versus dZ, curvature < 15
  n = 642462 

  Weighted least-squares fit:  Y = 45.1 + 0.203 X  + 0.00025 X**2 

curvature versus dZ, slope < 10
  n = 2750 
  X=0, Y = 48.79 +/- 23.60 
  Weighted least-squares fit:  Y = 48.7 + -0.552 X  + 0.22404 X**2 


Number of samples 861842
Max dz = 900
Mean dz = 53
RMS dz = 66.5732679084
100cm = 89.4589727583 percentile value of dz