curvature versus slope
  n = 5025242 
  X=0, Y = 8.92 +/- 6.86 
  Weighted least-squares fit:  Y = 8.9 + 1.579 X  + -0.00898 X**2 

slope versus dZ, curvature < 5
  n = 144783 
  X=0, Y = 4.46 +/- 2.41 
  Weighted least-squares fit:  Y = 4.7 + 0.066 X  + 0.00089 X**2 
     at X = 100, Y = 20.2 
     effective RMSE xy = 30.9 

slope versus dZ, curvature < 15
  n = 497305 
  X=0, Y = 4.47 +/- 2.68 
  Weighted least-squares fit:  Y = 4.8 + 0.047 X  + 0.00146 X**2 

curvature versus dZ, slope < 10
  n = 1850351 
  X=0, Y = 5.02 +/- 3.29 
  Weighted least-squares fit:  Y = 4.8 + 0.118 X  + 0.00129 X**2 


Number of samples 5030566
Max dz = 900
Mean dz = 8
RMS dz = 16.1554944214
100cm = 99.8787611573 percentile value of dz
Mean dz (curv<=5) = 4
RMS dz (curv<=5) = 5.74456264654