curvature versus slope
  n = 6519441 
  X=0, Y = 39.19 +/- 20.33 
  Weighted least-squares fit:  Y = 40.5 + 0.970 X  + -0.00530 X**2 

slope versus dZ, curvature < 5
  n = 63070 
  X=0, Y = 5.69 +/- 0.52 
  Weighted least-squares fit:  Y = 3.3 + 0.315 X  + -0.00166 X**2 
     at X = 100, Y = 18.2 
     effective RMSE xy = 28.1 

slope versus dZ, curvature < 15
  n = 426124 
  X=0, Y = 5.27 +/- 1.46 
  Weighted least-squares fit:  Y = 3.2 + 0.310 X  + -0.00139 X**2 

curvature versus dZ, slope < 10
  n = 113034 
  X=0, Y = 4.99 +/- 2.60 
  Weighted least-squares fit:  Y = 4.8 + 0.122 X  + 0.00020 X**2 


Number of samples 6522997
Max dz = 900
Mean dz = 13
RMS dz = 18.2756668825
100cm = 99.9308140108 percentile value of dz
Mean dz (curv<=5) = 9
RMS dz (curv<=5) = 12.5299640861