curvature versus slope
  n = 582302 
  X=0, Y = 24.82 +/- 19.63 
  Weighted least-squares fit:  Y = 65.2 + 1.586 X  + -0.01644 X**2 

slope versus dZ, curvature < 5
  n = 14583 

  Weighted least-squares fit:  Y = 8.1 + 0.224 X  + 0.00121 X**2 
     at X = 100, Y = 42.6 
     effective RMSE xy = 65.6 

slope versus dZ, curvature < 15
  n = 37719 

  Weighted least-squares fit:  Y = 7.1 + 0.404 X  + 0.00047 X**2 

curvature versus dZ, slope < 10
  n = 7028 
  X=0, Y = 9.81 +/- 6.63 
  Weighted least-squares fit:  Y = 10.1 + -0.382 X  + 0.27260 X**2 


Number of samples 593828
Max dz = 900
Mean dz = 62
RMS dz = 90.0499861188
100cm = 79.8556147571 percentile value of dz