curvature versus slope
  n = 192862 
  X=0, Y = 56.10 +/- 22.72 
  Weighted least-squares fit:  Y = 70.9 + 1.264 X  + -0.01336 X**2 

slope versus dZ, curvature < 5
  n = 19873 

  Weighted least-squares fit:  Y = 22.0 + -0.031 X  + 0.00680 X**2 
     at X = 100, Y = 87.0 
     effective RMSE xy = 132.2 

slope versus dZ, curvature < 15
  n = 53787 

  Weighted least-squares fit:  Y = 23.9 + 0.057 X  + 0.00634 X**2 

curvature versus dZ, slope < 10
  n = 252 
  X=0, Y = 20.26 +/- 7.82 
  Weighted least-squares fit:  Y = 23.2 + 1.553 X  + -0.08949 X**2 


Number of samples 194388
Max dz = 900
Mean dz = 81
RMS dz = 138.0
100cm = 71.4308496409 percentile value of dz
Mean dz (curv<=5) = 37
RMS dz (curv<=5) = 86.0697391654