curvature versus slope
  n = 479832 
  X=0, Y = 53.37 +/- 27.99 
  Weighted least-squares fit:  Y = 66.5 + 1.474 X  + -0.01579 X**2 

slope versus dZ, curvature < 5
  n = 50807 

  Weighted least-squares fit:  Y = 46.9 + 0.606 X  + -0.00350 X**2 
     at X = 100, Y = 72.4 
     effective RMSE xy = 86.8 

slope versus dZ, curvature < 15
  n = 159242 

  Weighted least-squares fit:  Y = 49.5 + 0.557 X  + -0.00282 X**2 

curvature versus dZ, slope < 10
  n = 3737 
  X=0, Y = 48.52 +/- 16.39 
  Weighted least-squares fit:  Y = 44.6 + 2.783 X  + -0.08879 X**2 


Number of samples 482660
Max dz = 900
Mean dz = 76
RMS dz = 108.485022008
100cm = 75.6085028799 percentile value of dz