curvature versus slope
  n = 543861 
  X=0, Y = 40.78 +/- 15.86 
  Weighted least-squares fit:  Y = 45.4 + 2.441 X  + -0.02605 X**2 

slope versus dZ, curvature < 5
  n = 285622 

  Weighted least-squares fit:  Y = 21.9 + -0.153 X  + 0.00346 X**2 
     at X = 100, Y = 41.2 
     effective RMSE xy = 54.8 

slope versus dZ, curvature < 15
  n = 401946 

  Weighted least-squares fit:  Y = 22.3 + -0.157 X  + 0.00407 X**2 

curvature versus dZ, slope < 10
  n = 7530 
  X=0, Y = 18.39 +/- 9.90 
  Weighted least-squares fit:  Y = 18.4 + 0.569 X  + 0.12252 X**2 


Number of samples 555825
Max dz = 800
Mean dz = 28
RMS dz = 44.1021541424
100cm = 96.0429991454 percentile value of dz