curvature versus slope
  n = 293359 
  X=0, Y = 20.00 +/- 16.41 
  Weighted least-squares fit:  Y = 50.2 + 2.370 X  + -0.02543 X**2 

slope versus dZ, curvature < 5
  n = 31082 

  Weighted least-squares fit:  Y = 83.0 + 0.177 X  + 0.00082 X**2 
     at X = 100, Y = 108.9 
     effective RMSE xy = 110.8 

slope versus dZ, curvature < 15
  n = 59289 

  Weighted least-squares fit:  Y = 80.8 + 0.307 X  + -0.00014 X**2 

curvature versus dZ, slope < 10
  n = 24659 
  X=0, Y = 87.81 +/- 48.11 
  Weighted least-squares fit:  Y = 84.9 + -0.652 X  + -0.16407 X**2 


Number of samples 297347
Max dz = 900
Mean dz = 96
RMS dz = 128.553490812
100cm = 59.2580385879 percentile value of dz