curvature versus slope
  n = 134725 
  X=0, Y = 58.45 +/- 21.39 
  Weighted least-squares fit:  Y = 64.9 + 1.625 X  + -0.01741 X**2 

slope versus dZ, curvature < 5
  n = 45562 

  Weighted least-squares fit:  Y = 7.5 + 0.665 X  + -0.00087 X**2 
     at X = 100, Y = 65.3 
     effective RMSE xy = 101.9 

slope versus dZ, curvature < 15
  n = 88316 

  Weighted least-squares fit:  Y = 10.0 + 0.604 X  + -0.00011 X**2 

curvature versus dZ, slope < 10
  n = 788 
  X=0, Y = 11.30 +/- 7.23 
  Weighted least-squares fit:  Y = 11.3 + 4.045 X  + -0.31838 X**2 


Number of samples 135871
Max dz = 900
Mean dz = 53
RMS dz = 102.985435864
100cm = 91.6744559177 percentile value of dz