curvature versus slope
  n = 2807658 
  X=0, Y = 8.56 +/- 7.41 
  Weighted least-squares fit:  Y = 16.4 + 3.973 X  + -0.06271 X**2 

slope versus dZ, curvature < 5
  n = 780548 
  X=0, Y = 4.97 +/- 3.75 
  Weighted least-squares fit:  Y = 4.3 + 0.322 X  + 0.00199 X**2 
     at X = 100, Y = 56.4 
     effective RMSE xy = 88.3 

slope versus dZ, curvature < 15
  n = 1337655 
  X=0, Y = 5.05 +/- 3.65 
  Weighted least-squares fit:  Y = 4.6 + 0.360 X  + 0.00136 X**2 

curvature versus dZ, slope < 10
  n = 1055641 
  X=0, Y = 5.41 +/- 3.87 
  Weighted least-squares fit:  Y = 3.8 + 2.271 X  + -0.02935 X**2 


Number of samples 2884173
Max dz = 600
Mean dz = 21
RMS dz = 37.762415177
100cm = 95.8461923054 percentile value of dz