curvature versus slope
  n = 475843 
  X=0, Y = 13.06 +/- 11.74 
  Weighted least-squares fit:  Y = 19.8 + 4.453 X  + -0.05158 X**2 

slope versus dZ, curvature < 5
  n = 394347 
  X=0, Y = 5.35 +/- 6.47 
  Weighted least-squares fit:  Y = 21.1 + 0.137 X  + 0.00529 X**2 
     at X = 100, Y = 87.6 
     effective RMSE xy = 133.6 

slope versus dZ, curvature < 15
  n = 421738 
  X=0, Y = 5.36 +/- 6.47 
  Weighted least-squares fit:  Y = 20.3 + 0.255 X  + 0.00488 X**2 

curvature versus dZ, slope < 10
  n = 344507 
  X=0, Y = 21.68 +/- 15.95 
  Weighted least-squares fit:  Y = 22.0 + 1.703 X  + 0.01932 X**2 


Number of samples 481686
Max dz = 900
Mean dz = 31
RMS dz = 74.966659256
100cm = 95.314790133 percentile value of dz
Mean dz (curv<=5) = 19
RMS dz (curv<=5) = 29.7825452237