curvature versus slope
  n = 318268 
  X=0, Y = 60.25 +/- 25.35 
  Weighted least-squares fit:  Y = 74.9 + 1.296 X  + -0.01493 X**2 

slope versus dZ, curvature < 5
  n = 128040 

  Weighted least-squares fit:  Y = 15.0 + 0.334 X  + 0.00178 X**2 
     at X = 100, Y = 66.1 
     effective RMSE xy = 101.2 

slope versus dZ, curvature < 15
  n = 225968 

  Weighted least-squares fit:  Y = 14.4 + 0.414 X  + 0.00139 X**2 

curvature versus dZ, slope < 10
  n = 2875 
  X=0, Y = 18.54 +/- 11.15 
  Weighted least-squares fit:  Y = 18.4 + 1.336 X  + 0.42456 X**2 


Number of samples 321588
Max dz = 900
Mean dz = 53
RMS dz = 77.3498545571
100cm = 91.1162729953 percentile value of dz