curvature versus slope
  n = 65145 
  X=0, Y = 28.53 +/- 21.07 
  Weighted least-squares fit:  Y = 47.8 + 2.350 X  + -0.02511 X**2 

slope versus dZ, curvature < 5
  n = 7055 

  Weighted least-squares fit:  Y = 21.4 + 0.072 X  + 0.00149 X**2 
     at X = 100, Y = 43.5 
     effective RMSE xy = 59.5 

slope versus dZ, curvature < 15
  n = 18663 

  Weighted least-squares fit:  Y = 24.7 + -0.071 X  + 0.00374 X**2 

curvature versus dZ, slope < 10
  n = 4109 
  X=0, Y = 21.13 +/- 11.41 
  Weighted least-squares fit:  Y = 20.6 + 2.583 X  + 0.01337 X**2 


Number of samples 66320
Max dz = 900
Mean dz = 48
RMS dz = 83.2946576918
100cm = 87.9282267793 percentile value of dz