curvature versus slope
  n = 506944 
  X=0, Y = 66.58 +/- 33.95 
  Weighted least-squares fit:  Y = 78.8 + 0.761 X  + -0.00768 X**2 

slope versus dZ, curvature < 5
  n = 39911 

  Weighted least-squares fit:  Y = 2.9 + 1.177 X  + -0.00724 X**2 
     at X = 100, Y = 48.2 
     effective RMSE xy = 75.6 

slope versus dZ, curvature < 15
  n = 136911 

  Weighted least-squares fit:  Y = 4.7 + 1.108 X  + -0.00617 X**2 

curvature versus dZ, slope < 10
  n = 4765 
  X=0, Y = 9.09 +/- 5.89 
  Weighted least-squares fit:  Y = 8.6 + 2.097 X  + -0.01034 X**2 


Number of samples 512201
Max dz = 900
Mean dz = 54
RMS dz = 80.6101730553
100cm = 85.5796845379 percentile value of dz