curvature versus slope
  n = 421999 
  X=0, Y = 46.94 +/- 30.65 
  Weighted least-squares fit:  Y = 66.6 + 1.262 X  + -0.01326 X**2 

slope versus dZ, curvature < 5
  n = 28437 

  Weighted least-squares fit:  Y = 7.6 + 0.515 X  + 0.00242 X**2 
     at X = 100, Y = 83.3 
     effective RMSE xy = 130.3 

slope versus dZ, curvature < 15
  n = 82750 

  Weighted least-squares fit:  Y = 7.8 + 0.592 X  + 0.00140 X**2 

curvature versus dZ, slope < 10
  n = 4260 
  X=0, Y = 11.67 +/- 6.92 
  Weighted least-squares fit:  Y = 10.3 + 2.799 X  + -0.06359 X**2 


Number of samples 432829
Max dz = 900
Mean dz = 67
RMS dz = 97.205966895
100cm = 77.4564550897 percentile value of dz