curvature versus slope
  n = 1216764 
  X=0, Y = 24.69 +/- 17.47 
  Weighted least-squares fit:  Y = 20.2 + 1.697 X  + -0.01198 X**2 

slope versus dZ, curvature < 5
  n = 22818 

  Weighted least-squares fit:  Y = 2.7 + 0.167 X  + -0.00003 X**2 
     at X = 100, Y = 19.0 
     effective RMSE xy = 29.6 

slope versus dZ, curvature < 15
  n = 103257 

  Weighted least-squares fit:  Y = 3.2 + 0.113 X  + 0.00093 X**2 

curvature versus dZ, slope < 10
  n = 241917 
  X=0, Y = 3.97 +/- 2.23 
  Weighted least-squares fit:  Y = 3.8 + 0.111 X  + 0.00159 X**2 


Number of samples 1218933
Max dz = 900
Mean dz = 10
RMS dz = 20.2977831302
100cm = 99.7895700584 percentile value of dz
Mean dz (curv<=5) = 4
RMS dz (curv<=5) = 6.5574385243