curvature versus slope
  n = 285971 
  X=0, Y = 59.34 +/- 18.19 
  Weighted least-squares fit:  Y = 66.6 + 1.603 X  + -0.01767 X**2 

slope versus dZ, curvature < 5
  n = 148314 

  Weighted least-squares fit:  Y = 10.4 + 0.110 X  + 0.00091 X**2 
     at X = 100, Y = 30.6 
     effective RMSE xy = 45.1 

slope versus dZ, curvature < 15
  n = 236277 

  Weighted least-squares fit:  Y = 13.3 + 0.046 X  + 0.00124 X**2 

curvature versus dZ, slope < 10
  n = 337 
  X=0, Y = 6.78 +/- 4.43 
  Weighted least-squares fit:  Y = 6.9 + 1.847 X  + -0.25910 X**2 


Number of samples 290512
Max dz = 900
Mean dz = 21
RMS dz = 38.4577690461
100cm = 97.6713526464 percentile value of dz