curvature versus slope
  n = 889126 
  X=0, Y = 36.92 +/- 31.83 
  Weighted least-squares fit:  Y = 66.6 + 1.370 X  + -0.01402 X**2 

slope versus dZ, curvature < 5
  n = 19449 

  Weighted least-squares fit:  Y = 9.7 + 0.530 X  + 0.00004 X**2 
     at X = 100, Y = 63.0 
     effective RMSE xy = 97.8 

slope versus dZ, curvature < 15
  n = 69724 

  Weighted least-squares fit:  Y = 10.3 + 0.531 X  + -0.00049 X**2 

curvature versus dZ, slope < 10
  n = 10767 
  X=0, Y = 12.79 +/- 7.34 
  Weighted least-squares fit:  Y = 11.8 + 1.654 X  + 0.05325 X**2 


Number of samples 897671
Max dz = 900
Mean dz = 57
RMS dz = 79.2779919019
100cm = 82.2027223782 percentile value of dz