curvature versus slope
  n = 469546 
  X=0, Y = 40.62 +/- 20.50 
  Weighted least-squares fit:  Y = 46.3 + 2.392 X  + -0.02526 X**2 

slope versus dZ, curvature < 5
  n = 123535 

  Weighted least-squares fit:  Y = 58.5 + -0.964 X  + 0.01050 X**2 
     at X = 100, Y = 67.1 
     effective RMSE xy = 51.6 

slope versus dZ, curvature < 15
  n = 280330 

  Weighted least-squares fit:  Y = 57.0 + -0.800 X  + 0.00919 X**2 

curvature versus dZ, slope < 10
  n = 8863 
  X=0, Y = 52.31 +/- 24.57 
  Weighted least-squares fit:  Y = 51.4 + 0.716 X  + 0.06415 X**2 


Number of samples 476276
Max dz = 900
Mean dz = 49
RMS dz = 75.6108457829
100cm = 90.6932114992 percentile value of dz