curvature versus slope
  n = 872777 
  X=0, Y = 6.75 +/- 4.45 
  Weighted least-squares fit:  Y = 5.3 + 1.735 X  + -0.01031 X**2 

slope versus dZ, curvature < 5
  n = 125780 
  X=0, Y = 7.76 +/- 5.60 
  Weighted least-squares fit:  Y = 6.0 + 0.124 X  + -0.00148 X**2 
     at X = 100, Y = 3.6 
     Bad fit. P2 = 0
slope versus dZ, curvature < 15
  n = 301799 
  X=0, Y = 7.32 +/- 4.96 
  Weighted least-squares fit:  Y = 6.5 + 0.039 X  + 0.00018 X**2 

curvature versus dZ, slope < 10
  n = 584838 
  X=0, Y = 6.52 +/- 4.31 
  Weighted least-squares fit:  Y = 6.3 + 0.093 X  + 0.00092 X**2 


Number of samples 873204
Max dz = 900
Mean dz = 6
RMS dz = 13.2664991614
100cm = 99.9453735897 percentile value of dz
Mean dz (curv<=5) = 5
RMS dz (curv<=5) = 7.87400787401