curvature versus slope
  n = 710631 
  X=0, Y = 40.36 +/- 21.93 
  Weighted least-squares fit:  Y = 38.2 + 1.049 X  + -0.00645 X**2 

slope versus dZ, curvature < 5
  n = 6557 

  Weighted least-squares fit:  Y = 4.0 + 0.039 X  + 0.00140 X**2 
     at X = 100, Y = 22.0 
     effective RMSE xy = 33.9 

slope versus dZ, curvature < 15
  n = 31416 

  Weighted least-squares fit:  Y = 4.6 + -0.007 X  + 0.00228 X**2 

curvature versus dZ, slope < 10
  n = 24505 
  X=0, Y = 5.00 +/- 2.66 
  Weighted least-squares fit:  Y = 4.2 + 0.111 X  + 0.00136 X**2 


Number of samples 713145
Max dz = 900
Mean dz = 14
RMS dz = 26.1533936612
100cm = 99.5871807276 percentile value of dz
Mean dz (curv<=5) = 6
RMS dz (curv<=5) = 9.43398113206