curvature versus slope
  n = 79008 
  X=0, Y = 74.00 +/- 26.91 
  Weighted least-squares fit:  Y = 75.6 + 1.142 X  + -0.01193 X**2 

slope versus dZ, curvature < 5
  n = 8005 

  Weighted least-squares fit:  Y = 31.0 + 0.565 X  + -0.00144 X**2 
     at X = 100, Y = 73.1 
     effective RMSE xy = 104.1 

slope versus dZ, curvature < 15
  n = 22219 

  Weighted least-squares fit:  Y = 34.6 + 0.420 X  + 0.00061 X**2 

curvature versus dZ, slope < 10
  n = 153 
  X=0, Y = 39.99 +/- 28.58 
  Weighted least-squares fit:  Y = 40.1 + 4.879 X  + -0.68264 X**2 


Number of samples 80421
Max dz = 900
Mean dz = 88
RMS dz = 142.856571427
100cm = 73.5156240285 percentile value of dz
Mean dz (curv<=5) = 51
RMS dz (curv<=5) = 63.2455532034