curvature versus slope
  n = 5041639 
  X=0, Y = 30.96 +/- 16.58 
  Weighted least-squares fit:  Y = 31.2 + 0.900 X  + -0.00365 X**2 

slope versus dZ, curvature < 5
  n = 35723 

  Weighted least-squares fit:  Y = 2.3 + 0.170 X  + 0.00025 X**2 
     at X = 100, Y = 21.8 
     effective RMSE xy = 34.1 

slope versus dZ, curvature < 15
  n = 191429 
  X=0, Y = 3.61 +/- 2.96 
  Weighted least-squares fit:  Y = 3.1 + 0.147 X  + 0.00092 X**2 

curvature versus dZ, slope < 10
  n = 121519 
  X=0, Y = 3.85 +/- 2.35 
  Weighted least-squares fit:  Y = 4.6 + 0.190 X  + 0.00011 X**2 


Number of samples 5047458
Max dz = 900
Mean dz = 13
RMS dz = 19.4935886896
100cm = 99.8558482309 percentile value of dz
Mean dz (curv<=5) = 5
RMS dz (curv<=5) = 8.0