curvature versus slope
  n = 508079 
  X=0, Y = 45.88 +/- 27.51 
  Weighted least-squares fit:  Y = 58.3 + 1.772 X  + -0.01836 X**2 

slope versus dZ, curvature < 5
  n = 38706 

  Weighted least-squares fit:  Y = 31.8 + 0.938 X  + -0.00257 X**2 
     at X = 100, Y = 99.9 
     effective RMSE xy = 148.7 

slope versus dZ, curvature < 15
  n = 123707 

  Weighted least-squares fit:  Y = 32.1 + 0.958 X  + -0.00262 X**2 

curvature versus dZ, slope < 10
  n = 5404 
  X=0, Y = 40.27 +/- 13.77 
  Weighted least-squares fit:  Y = 42.4 + -0.869 X  + 0.25045 X**2 


Number of samples 511842
Max dz = 900
Mean dz = 77
RMS dz = 109.352640572
100cm = 73.9091360224 percentile value of dz