curvature versus slope
  n = 221750 
  X=0, Y = 50.26 +/- 20.77 
  Weighted least-squares fit:  Y = 55.7 + 2.326 X  + -0.02720 X**2 

slope versus dZ, curvature < 5
  n = 127231 

  Weighted least-squares fit:  Y = 8.8 + 0.649 X  + -0.00140 X**2 
     at X = 100, Y = 59.7 
     effective RMSE xy = 92.8 

slope versus dZ, curvature < 15
  n = 184152 

  Weighted least-squares fit:  Y = 8.7 + 0.714 X  + -0.00183 X**2 

curvature versus dZ, slope < 10
  n = 1159 
  X=0, Y = 18.52 +/- 8.57 
  Weighted least-squares fit:  Y = 17.8 + 1.786 X  + -0.25367 X**2 


Number of samples 222777
Max dz = 900
Mean dz = 39
RMS dz = 85.5102333057
100cm = 97.5347544854 percentile value of dz