curvature versus slope
  n = 246000 
  X=0, Y = 34.64 +/- 25.05 
  Weighted least-squares fit:  Y = 63.0 + 1.634 X  + -0.01697 X**2 

slope versus dZ, curvature < 5
  n = 15286 

  Weighted least-squares fit:  Y = 10.1 + 0.768 X  + -0.00048 X**2 
     at X = 100, Y = 82.2 
     effective RMSE xy = 128.2 

slope versus dZ, curvature < 15
  n = 39625 

  Weighted least-squares fit:  Y = 10.1 + 0.854 X  + -0.00091 X**2 

curvature versus dZ, slope < 10
  n = 5032 
  X=0, Y = 12.58 +/- 7.27 
  Weighted least-squares fit:  Y = 12.0 + 2.664 X  + -0.05518 X**2 


Number of samples 250389
Max dz = 900
Mean dz = 79
RMS dz = 120.42009799
100cm = 72.8809971684 percentile value of dz