curvature versus slope
  n = 321576 
  X=0, Y = 40.01 +/- 19.50 
  Weighted least-squares fit:  Y = 49.5 + 2.567 X  + -0.02910 X**2 

slope versus dZ, curvature < 5
  n = 152629 

  Weighted least-squares fit:  Y = 14.6 + 0.385 X  + 0.00263 X**2 
     at X = 100, Y = 79.5 
     effective RMSE xy = 122.7 

slope versus dZ, curvature < 15
  n = 231815 

  Weighted least-squares fit:  Y = 15.4 + 0.358 X  + 0.00328 X**2 

curvature versus dZ, slope < 10
  n = 10762 
  X=0, Y = 15.93 +/- 9.69 
  Weighted least-squares fit:  Y = 15.5 + 2.194 X  + -0.33589 X**2 


Number of samples 325172
Max dz = 900
Mean dz = 41
RMS dz = 69.5485441976
100cm = 92.1158648346 percentile value of dz