curvature versus slope
  n = 382632300 
  X=0, Y = 28.50 +/- 24.43 
  Weighted least-squares fit:  Y = 49.0 + 2.548 X  + -0.02760 X**2 

slope versus dZ, curvature < 5
  n = 62605504 
  X=0, Y = 9.08 +/- 10.12 
  Weighted least-squares fit:  Y = 19.1 + 0.693 X  + -0.00245 X**2 
     at X = 100, Y = 63.8 
     effective RMSE xy = 95.7 

slope versus dZ, curvature < 15
  n = 123794750 
  X=0, Y = 9.37 +/- 10.41 
  Weighted least-squares fit:  Y = 20.0 + 0.625 X  + -0.00163 X**2 

curvature versus dZ, slope < 10
  n = 45616526 
  X=0, Y = 21.56 +/- 18.16 
  Weighted least-squares fit:  Y = 19.2 + 3.049 X  + -0.02559 X**2 


Number of samples 387413828
Max dz = 900
Mean dz = 48
RMS dz = 80.3741251896
100cm = 86.9293669094 percentile value of dz
Mean dz (curv<=5) = 22
RMS dz (curv<=5) = 37.775653535