curvature versus slope
  n = 525022 
  X=0, Y = 40.07 +/- 28.37 
  Weighted least-squares fit:  Y = 61.1 + 1.621 X  + -0.01673 X**2 

slope versus dZ, curvature < 5
  n = 23167 

  Weighted least-squares fit:  Y = 10.2 + 0.237 X  + 0.00245 X**2 
     at X = 100, Y = 58.4 
     effective RMSE xy = 90.3 

slope versus dZ, curvature < 15
  n = 77099 

  Weighted least-squares fit:  Y = 10.3 + 0.336 X  + 0.00200 X**2 

curvature versus dZ, slope < 10
  n = 8762 
  X=0, Y = 11.83 +/- 6.86 
  Weighted least-squares fit:  Y = 11.2 + 1.643 X  + 0.05300 X**2 


Number of samples 535223
Max dz = 900
Mean dz = 61
RMS dz = 92.0163029033
100cm = 80.4094741818 percentile value of dz