curvature versus slope
  n = 326834 
  X=0, Y = 53.66 +/- 26.18 
  Weighted least-squares fit:  Y = 64.3 + 1.393 X  + -0.01410 X**2 

slope versus dZ, curvature < 5
  n = 42203 

  Weighted least-squares fit:  Y = 11.8 + 0.194 X  + 0.00173 X**2 
     at X = 100, Y = 48.5 
     effective RMSE xy = 73.8 

slope versus dZ, curvature < 15
  n = 113741 

  Weighted least-squares fit:  Y = 13.6 + 0.169 X  + 0.00211 X**2 

curvature versus dZ, slope < 10
  n = 2542 
  X=0, Y = 12.85 +/- 9.99 
  Weighted least-squares fit:  Y = 11.5 + 1.904 X  + 0.05393 X**2 


Number of samples 333420
Max dz = 900
Mean dz = 51
RMS dz = 80.6721761204
100cm = 86.5946853818 percentile value of dz