curvature versus slope
  n = 667602 
  X=0, Y = 56.72 +/- 21.42 
  Weighted least-squares fit:  Y = 62.7 + 1.423 X  + -0.01500 X**2 

slope versus dZ, curvature < 5
  n = 117755 

  Weighted least-squares fit:  Y = 2.2 + 4.578 X  + -0.03042 X**2 
     at X = 100, Y = 155.7 
     effective RMSE xy = 244.6 

slope versus dZ, curvature < 15
  n = 315745 

  Weighted least-squares fit:  Y = 20.2 + 3.527 X  + -0.02376 X**2 

curvature versus dZ, slope < 10
  n = 2609 
  X=0, Y = 60.64 +/- 75.18 
  Weighted least-squares fit:  Y = 58.2 + -6.749 X  + 0.26277 X**2 


Number of samples 690992
Max dz = 900
Mean dz = 86
RMS dz = 162.040118489
100cm = 80.1132285178 percentile value of dz