curvature versus slope
  n = 613612 
  X=0, Y = 26.75 +/- 23.19 
  Weighted least-squares fit:  Y = 62.2 + 1.832 X  + -0.01994 X**2 

slope versus dZ, curvature < 5
  n = 46969 

  Weighted least-squares fit:  Y = 20.6 + 1.047 X  + -0.00392 X**2 
     at X = 100, Y = 86.0 
     effective RMSE xy = 131.2 

slope versus dZ, curvature < 15
  n = 112285 

  Weighted least-squares fit:  Y = 22.2 + 1.068 X  + -0.00380 X**2 

curvature versus dZ, slope < 10
  n = 24705 
  X=0, Y = 23.02 +/- 18.31 
  Weighted least-squares fit:  Y = 27.2 + 3.945 X  + -0.12292 X**2 


Number of samples 617780
Max dz = 900
Mean dz = 77
RMS dz = 115.0
100cm = 71.3671533556 percentile value of dz