curvature versus slope
  n = 553520 
  X=0, Y = 44.17 +/- 31.90 
  Weighted least-squares fit:  Y = 69.1 + 1.241 X  + -0.01202 X**2 

slope versus dZ, curvature < 5
  n = 9817 

  Weighted least-squares fit:  Y = 15.3 + 1.413 X  + -0.00704 X**2 
     at X = 100, Y = 86.2 
     effective RMSE xy = 133.2 

slope versus dZ, curvature < 15
  n = 44641 

  Weighted least-squares fit:  Y = 17.6 + 1.330 X  + -0.00607 X**2 

curvature versus dZ, slope < 10
  n = 3277 
  X=0, Y = 26.70 +/- 23.83 
  Weighted least-squares fit:  Y = 18.8 + 3.571 X  + -0.02143 X**2 


Number of samples 558336
Max dz = 900
Mean dz = 82
RMS dz = 122.926807491
100cm = 69.268146779 percentile value of dz