curvature versus slope
  n = 313230 
  X=0, Y = 48.73 +/- 36.49 
  Weighted least-squares fit:  Y = 72.0 + 1.006 X  + -0.00969 X**2 

slope versus dZ, curvature < 5
  n = 8688 

  Weighted least-squares fit:  Y = 13.5 + 0.567 X  + 0.00124 X**2 
     at X = 100, Y = 82.6 
     effective RMSE xy = 127.9 

slope versus dZ, curvature < 15
  n = 26341 

  Weighted least-squares fit:  Y = 12.7 + 0.718 X  + 0.00008 X**2 

curvature versus dZ, slope < 10
  n = 1453 
  X=0, Y = 20.50 +/- 9.26 
  Weighted least-squares fit:  Y = 17.8 + 2.676 X  + -0.03097 X**2 


Number of samples 316866
Max dz = 900
Mean dz = 82
RMS dz = 118.882294729
100cm = 69.7354717767 percentile value of dz