curvature versus slope
  n = 1468098 
  X=0, Y = 51.62 +/- 32.91 
  Weighted least-squares fit:  Y = 58.3 + 0.933 X  + -0.00767 X**2 

slope versus dZ, curvature < 5
  n = 20469 

  Weighted least-squares fit:  Y = 6.2 + 0.137 X  + 0.00021 X**2 
     at X = 100, Y = 22.0 
     effective RMSE xy = 33.2 

slope versus dZ, curvature < 15
  n = 85915 
  X=0, Y = 5.39 +/- 2.88 
  Weighted least-squares fit:  Y = 6.4 + 0.104 X  + 0.00096 X**2 

curvature versus dZ, slope < 10
  n = 45263 
  X=0, Y = 7.66 +/- 3.86 
  Weighted least-squares fit:  Y = 6.9 + 0.139 X  + -0.00163 X**2 


Number of samples 1475853
Max dz = 900
Mean dz = 6226
RMS dz = 11442.9587083
100cm = 99.238880837 percentile value of dz
Mean dz (curv<=5) = 1170
RMS dz (curv<=5) = 5434.7421282