curvature versus slope
  n = 2676856 
  X=0, Y = 33.24 +/- 26.64 
  Weighted least-squares fit:  Y = 73.6 + 1.276 X  + -0.01304 X**2 

slope versus dZ, curvature < 5
  n = 37434 

  Weighted least-squares fit:  Y = 12.9 + 0.047 X  + 0.00156 X**2 
     at X = 100, Y = 33.2 
     effective RMSE xy = 48.1 

slope versus dZ, curvature < 15
  n = 250314 

  Weighted least-squares fit:  Y = 12.9 + 0.081 X  + 0.00145 X**2 

curvature versus dZ, slope < 10
  n = 14594 
  X=0, Y = 13.39 +/- 7.91 
  Weighted least-squares fit:  Y = 13.1 + 1.118 X  + -0.15437 X**2 


Number of samples 2714984
Max dz = 900
Mean dz = 45
RMS dz = 64.1014820421
100cm = 89.0206351124 percentile value of dz