curvature versus slope
  n = 144948 
  X=0, Y = 38.63 +/- 24.65 
  Weighted least-squares fit:  Y = 62.9 + 1.609 X  + -0.01688 X**2 

slope versus dZ, curvature < 5
  n = 21807 

  Weighted least-squares fit:  Y = 92.4 + -0.172 X  + 0.00341 X**2 
     at X = 100, Y = 109.3 
     effective RMSE xy = 91.7 

slope versus dZ, curvature < 15
  n = 42225 

  Weighted least-squares fit:  Y = 91.4 + -0.067 X  + 0.00252 X**2 

curvature versus dZ, slope < 10
  n = 3371 
  X=0, Y = 89.62 +/- 11.65 
  Weighted least-squares fit:  Y = 88.3 + 1.193 X  + -0.12121 X**2 


Number of samples 146397
Max dz = 900
Mean dz = 116
RMS dz = 146.348898185
100cm = 58.0291945873 percentile value of dz