curvature versus slope
  n = 4694212 
  X=0, Y = 39.29 +/- 22.97 
  Weighted least-squares fit:  Y = 38.3 + 1.063 X  + -0.00607 X**2 

slope versus dZ, curvature < 5
  n = 30884 

  Weighted least-squares fit:  Y = 1.2 + 0.269 X  + -0.00075 X**2 
     at X = 100, Y = 20.7 
     effective RMSE xy = 32.5 

slope versus dZ, curvature < 15
  n = 218264 

  Weighted least-squares fit:  Y = 1.8 + 0.233 X  + 0.00015 X**2 

curvature versus dZ, slope < 10
  n = 234808 
  X=0, Y = 3.23 +/- 2.06 
  Weighted least-squares fit:  Y = 3.3 + 0.157 X  + -0.00020 X**2 


Number of samples 4701415
Max dz = 900
Mean dz = 29
RMS dz = 459.117631986
100cm = 99.9078362578 percentile value of dz
Mean dz (curv<=5) = 7
RMS dz (curv<=5) = 10.1488915651