curvature versus slope
  n = 21750289 
  X=0, Y = 17.36 +/- 10.61 
  Weighted least-squares fit:  Y = 39.8 + 3.161 X  + -0.03424 X**2 

slope versus dZ, curvature < 5
  n = 151646 

  Weighted least-squares fit:  Y = 19.7 + 0.204 X  + -0.00168 X**2 
     at X = 100, Y = 23.4 
     effective RMSE xy = 19.7 

slope versus dZ, curvature < 15
  n = 2163379 

  Weighted least-squares fit:  Y = 19.7 + 0.331 X  + -0.00116 X**2 

curvature versus dZ, slope < 10
  n = 149549 
  X=0, Y = 21.89 +/- 12.67 
  Weighted least-squares fit:  Y = 21.4 + 0.578 X  + 0.06776 X**2 


Number of samples 22090450
Max dz = 900
Mean dz = 38
RMS dz = 53.310411741
100cm = 93.0622418285 percentile value of dz