curvature versus slope
  n = 304434 
  X=0, Y = 40.21 +/- 23.71 
  Weighted least-squares fit:  Y = 52.1 + 2.277 X  + -0.02313 X**2 

slope versus dZ, curvature < 5
  n = 181659 

  Weighted least-squares fit:  Y = 7.7 + 0.505 X  + -0.00108 X**2 
     at X = 100, Y = 47.5 
     effective RMSE xy = 73.5 

slope versus dZ, curvature < 15
  n = 254357 

  Weighted least-squares fit:  Y = 7.6 + 0.546 X  + -0.00119 X**2 

curvature versus dZ, slope < 10
  n = 20163 
  X=0, Y = 12.30 +/- 7.23 
  Weighted least-squares fit:  Y = 12.1 + 1.042 X  + 0.14716 X**2 


Number of samples 308042
Max dz = 900
Mean dz = 27
RMS dz = 44.6989932773
100cm = 97.8405542101 percentile value of dz