curvature versus slope
  n = 477783 
  X=0, Y = 33.32 +/- 28.33 
  Weighted least-squares fit:  Y = 66.1 + 1.468 X  + -0.01581 X**2 

slope versus dZ, curvature < 5
  n = 24058 

  Weighted least-squares fit:  Y = 34.7 + 0.093 X  + 0.00395 X**2 
     at X = 100, Y = 83.5 
     effective RMSE xy = 119.3 

slope versus dZ, curvature < 15
  n = 62674 

  Weighted least-squares fit:  Y = 34.1 + 0.233 X  + 0.00266 X**2 

curvature versus dZ, slope < 10
  n = 13705 
  X=0, Y = 35.08 +/- 8.90 
  Weighted least-squares fit:  Y = 33.7 + 2.721 X  + -0.06343 X**2 


Number of samples 483461
Max dz = 900
Mean dz = 79
RMS dz = 119.824872209
100cm = 73.0536692722 percentile value of dz