curvature versus slope
  n = 208659 
  X=0, Y = 42.78 +/- 33.70 
  Weighted least-squares fit:  Y = 66.9 + 1.644 X  + -0.01735 X**2 

slope versus dZ, curvature < 5
  n = 42615 

  Weighted least-squares fit:  Y = 37.9 + 0.229 X  + 0.00427 X**2 
     at X = 100, Y = 103.4 
     effective RMSE xy = 151.1 

slope versus dZ, curvature < 15
  n = 98879 

  Weighted least-squares fit:  Y = 37.3 + 0.302 X  + 0.00425 X**2 

curvature versus dZ, slope < 10
  n = 21426 
  X=0, Y = 38.97 +/- 18.98 
  Weighted least-squares fit:  Y = 39.1 + 0.815 X  + -0.01998 X**2 


Number of samples 210841
Max dz = 900
Mean dz = 79
RMS dz = 115.602768133
100cm = 72.6884239783 percentile value of dz
Mean dz (curv<=5) = 50
RMS dz (curv<=5) = 68.7386354243