curvature versus slope
  n = 17669 
  X=0, Y = 15.33 +/- 8.30 
  Weighted least-squares fit:  Y = 15.1 + 1.615 X  + -0.00911 X**2 

slope versus dZ, curvature < 5
  n = 346 

  Weighted least-squares fit:  Y = 9.4 + -0.336 X  + 0.00912 X**2 
     at X = 100, Y = 67.0 
     effective RMSE xy = 104.2 

slope versus dZ, curvature < 15
  n = 1376 

  Weighted least-squares fit:  Y = 3.5 + 0.258 X  + -0.00073 X**2 

curvature versus dZ, slope < 10
  n = 2581 
  X=0, Y = 8.07 +/- 4.08 
  Weighted least-squares fit:  Y = 8.5 + -0.239 X  + 0.00859 X**2 


Number of samples 17713
Max dz = 300
Mean dz = 10
RMS dz = 17.9164728672
100cm = 99.7120758765 percentile value of dz
Mean dz (curv<=5) = 6
RMS dz (curv<=5) = 8.77496438739