curvature versus slope
  n = 1050846 
  X=0, Y = 67.05 +/- 22.28 
  Weighted least-squares fit:  Y = 76.4 + 1.318 X  + -0.01487 X**2 

slope versus dZ, curvature < 5
  n = 416298 

  Weighted least-squares fit:  Y = 3.6 + 0.465 X  + 0.00065 X**2 
     at X = 100, Y = 56.6 
     effective RMSE xy = 88.8 

slope versus dZ, curvature < 15
  n = 808353 

  Weighted least-squares fit:  Y = 4.0 + 0.477 X  + 0.00063 X**2 

curvature versus dZ, slope < 10
  n = 2989 
  X=0, Y = 6.17 +/- 3.94 
  Weighted least-squares fit:  Y = 5.8 + 1.621 X  + 0.05753 X**2 


Number of samples 1055286
Max dz = 800
Mean dz = 38
RMS dz = 48.3218377134
100cm = 97.2663334868 percentile value of dz