curvature versus slope
  n = 3762881 
  X=0, Y = 44.66 +/- 21.92 
  Weighted least-squares fit:  Y = 42.6 + 1.053 X  + -0.00686 X**2 

slope versus dZ, curvature < 5
  n = 27486 

  Weighted least-squares fit:  Y = 0.7 + 0.268 X  + -0.00023 X**2 
     at X = 100, Y = 25.3 
     effective RMSE xy = 39.7 

slope versus dZ, curvature < 15
  n = 182390 

  Weighted least-squares fit:  Y = 1.0 + 0.251 X  + 0.00029 X**2 

curvature versus dZ, slope < 10
  n = 124537 
  X=0, Y = 2.77 +/- 1.82 
  Weighted least-squares fit:  Y = 2.5 + 0.192 X  + -0.00079 X**2 


Number of samples 3834145
Max dz = 900
Mean dz = 254
RMS dz = 1741.90786209
100cm = 99.8980737557 percentile value of dz
Mean dz (curv<=5) = 23
RMS dz (curv<=5) = 388.542147006