curvature versus slope
  n = 1816332 
  X=0, Y = 30.45 +/- 21.14 
  Weighted least-squares fit:  Y = 29.5 + 1.488 X  + -0.01109 X**2 

slope versus dZ, curvature < 5
  n = 14257 

  Weighted least-squares fit:  Y = 1.6 + 0.144 X  + 0.00087 X**2 
     at X = 100, Y = 24.7 
     effective RMSE xy = 38.7 

slope versus dZ, curvature < 15
  n = 67184 
  X=0, Y = 3.54 +/- 0.71 
  Weighted least-squares fit:  Y = 1.8 + 0.140 X  + 0.00099 X**2 

curvature versus dZ, slope < 10
  n = 107319 
  X=0, Y = 2.86 +/- 1.71 
  Weighted least-squares fit:  Y = 2.2 + 0.196 X  + 0.00094 X**2 


Number of samples 1821916
Max dz = 900
Mean dz = 15
RMS dz = 23.8956062907
100cm = 99.6271507578 percentile value of dz
Mean dz (curv<=5) = 4
RMS dz (curv<=5) = 7.74596669241