curvature versus slope
  n = 309834 
  X=0, Y = 27.55 +/- 24.67 
  Weighted least-squares fit:  Y = 71.8 + 1.115 X  + -0.01125 X**2 

slope versus dZ, curvature < 5
  n = 8793 

  Weighted least-squares fit:  Y = 12.6 + 0.111 X  + 0.00385 X**2 
     at X = 100, Y = 62.3 
     effective RMSE xy = 95.9 

slope versus dZ, curvature < 15
  n = 19307 

  Weighted least-squares fit:  Y = 10.1 + 0.460 X  + 0.00088 X**2 

curvature versus dZ, slope < 10
  n = 5459 
  X=0, Y = 13.61 +/- 8.93 
  Weighted least-squares fit:  Y = 14.0 + 0.732 X  + -0.03184 X**2 


Number of samples 311818
Max dz = 900
Mean dz = 70
RMS dz = 104.718670733
100cm = 76.5725519373 percentile value of dz