curvature versus slope
  n = 250830 
  X=0, Y = 29.20 +/- 19.23 
  Weighted least-squares fit:  Y = 58.4 + 1.818 X  + -0.01986 X**2 

slope versus dZ, curvature < 5
  n = 24776 

  Weighted least-squares fit:  Y = 4.5 + 0.502 X  + 0.00126 X**2 
     at X = 100, Y = 67.3 
     effective RMSE xy = 105.4 

slope versus dZ, curvature < 15
  n = 45268 

  Weighted least-squares fit:  Y = 4.6 + 0.540 X  + 0.00111 X**2 

curvature versus dZ, slope < 10
  n = 6664 
  X=0, Y = 7.07 +/- 4.50 
  Weighted least-squares fit:  Y = 5.9 + 2.183 X  + 0.07593 X**2 


Number of samples 252698
Max dz = 900
Mean dz = 68
RMS dz = 102.371871137
100cm = 76.2154825127 percentile value of dz