curvature versus slope
  n = 489146 
  X=0, Y = 54.57 +/- 33.37 
  Weighted least-squares fit:  Y = 80.7 + 0.741 X  + -0.00729 X**2 

slope versus dZ, curvature < 5
  n = 6213 

  Weighted least-squares fit:  Y = 8.9 + 0.567 X  + 0.00150 X**2 
     at X = 100, Y = 80.6 
     effective RMSE xy = 125.9 

slope versus dZ, curvature < 15
  n = 26520 

  Weighted least-squares fit:  Y = 7.4 + 0.861 X  + -0.00071 X**2 

curvature versus dZ, slope < 10
  n = 394 
  X=0, Y = 13.44 +/- 8.34 
  Weighted least-squares fit:  Y = 11.7 + 4.991 X  + -0.21351 X**2 


Number of samples 498903
Max dz = 900
Mean dz = 96
RMS dz = 132.132509247
100cm = 62.7759303913 percentile value of dz