curvature versus slope
  n = 429498 
  X=0, Y = 35.15 +/- 32.04 
  Weighted least-squares fit:  Y = 64.7 + 1.370 X  + -0.01333 X**2 

slope versus dZ, curvature < 5
  n = 11999 

  Weighted least-squares fit:  Y = 5.7 + 0.421 X  + -0.00220 X**2 
     at X = 100, Y = 25.7 
     effective RMSE xy = 39.4 

slope versus dZ, curvature < 15
  n = 29286 

  Weighted least-squares fit:  Y = 6.8 + 0.379 X  + -0.00115 X**2 

curvature versus dZ, slope < 10
  n = 6789 
  X=0, Y = 7.41 +/- 5.02 
  Weighted least-squares fit:  Y = 6.4 + 2.400 X  + -0.04332 X**2 


Number of samples 433291
Max dz = 800
Mean dz = 48
RMS dz = 70.4272674466
100cm = 86.7811701605 percentile value of dz