curvature versus slope
  n = 10357895 
  X=0, Y = 26.09 +/- 17.41 
  Weighted least-squares fit:  Y = 53.5 + 2.279 X  + -0.02355 X**2 

slope versus dZ, curvature < 5
  n = 351947 

  Weighted least-squares fit:  Y = 8.6 + 0.297 X  + -0.00119 X**2 
     at X = 100, Y = 26.3 
     effective RMSE xy = 39.1 

slope versus dZ, curvature < 15
  n = 2769099 

  Weighted least-squares fit:  Y = 9.5 + 0.257 X  + -0.00031 X**2 

curvature versus dZ, slope < 10
  n = 42200 
  X=0, Y = 9.55 +/- 6.40 
  Weighted least-squares fit:  Y = 10.0 + 1.526 X  + -0.08990 X**2 


Number of samples 10522727
Max dz = 900
Mean dz = 26
RMS dz = 37.3363094052
100cm = 97.6523861163 percentile value of dz