curvature versus slope
  n = 2815346 
  X=0, Y = 15.78 +/- 10.65 
  Weighted least-squares fit:  Y = 59.1 + 1.975 X  + -0.01977 X**2 

slope versus dZ, curvature < 5
  n = 41892 

  Weighted least-squares fit:  Y = 12.5 + 0.784 X  + -0.00438 X**2 
     at X = 100, Y = 47.2 
     effective RMSE xy = 71.4 

slope versus dZ, curvature < 15
  n = 264499 

  Weighted least-squares fit:  Y = 15.6 + 0.643 X  + -0.00270 X**2 

curvature versus dZ, slope < 10
  n = 22269 
  X=0, Y = 16.15 +/- 9.38 
  Weighted least-squares fit:  Y = 16.4 + 1.292 X  + 0.16481 X**2 


Number of samples 2846415
Max dz = 900
Mean dz = 46
RMS dz = 64.3506021728
100cm = 89.2869802892 percentile value of dz