curvature versus slope
  n = 1768097 
  X=0, Y = 21.37 +/- 14.20 
  Weighted least-squares fit:  Y = 67.3 + 1.491 X  + -0.01521 X**2 

slope versus dZ, curvature < 5
  n = 27966 

  Weighted least-squares fit:  Y = 14.6 + 0.239 X  + -0.00001 X**2 
     at X = 100, Y = 38.5 
     effective RMSE xy = 55.9 

slope versus dZ, curvature < 15
  n = 73196 

  Weighted least-squares fit:  Y = 13.8 + 0.344 X  + -0.00006 X**2 

curvature versus dZ, slope < 10
  n = 8050 
  X=0, Y = 18.42 +/- 9.93 
  Weighted least-squares fit:  Y = 18.6 + 0.341 X  + 0.11473 X**2 


Number of samples 1786710
Max dz = 900
Mean dz = 87
RMS dz = 357.415724332
100cm = 85.8794096412 percentile value of dz