curvature versus slope
  n = 208833 
  X=0, Y = 35.87 +/- 21.01 
  Weighted least-squares fit:  Y = 56.3 + 1.917 X  + -0.02042 X**2 

slope versus dZ, curvature < 5
  n = 24395 

  Weighted least-squares fit:  Y = 11.7 + 1.056 X  + -0.00566 X**2 
     at X = 100, Y = 60.8 
     effective RMSE xy = 93.7 

slope versus dZ, curvature < 15
  n = 59095 

  Weighted least-squares fit:  Y = 13.5 + 0.871 X  + -0.00352 X**2 

curvature versus dZ, slope < 10
  n = 2802 
  X=0, Y = 20.52 +/- 10.97 
  Weighted least-squares fit:  Y = 19.9 + 0.744 X  + 0.03402 X**2 


Number of samples 210959
Max dz = 900
Mean dz = 65
RMS dz = 117.388244727
100cm = 80.8882294664 percentile value of dz