curvature versus slope
  n = 450443 
  X=0, Y = 21.83 +/- 14.54 
  Weighted least-squares fit:  Y = 45.6 + 2.510 X  + -0.02703 X**2 

slope versus dZ, curvature < 5
  n = 71488 

  Weighted least-squares fit:  Y = 12.6 + -0.074 X  + 0.00365 X**2 
     at X = 100, Y = 41.6 
     effective RMSE xy = 62.4 

slope versus dZ, curvature < 15
  n = 114292 

  Weighted least-squares fit:  Y = 11.3 + 0.062 X  + 0.00284 X**2 

curvature versus dZ, slope < 10
  n = 27378 
  X=0, Y = 13.84 +/- 8.23 
  Weighted least-squares fit:  Y = 11.9 + 1.388 X  + -0.01150 X**2 


Number of samples 454771
Max dz = 900
Mean dz = 45
RMS dz = 81.4616474177
100cm = 88.0561865202 percentile value of dz