curvature versus slope
  n = 772168 
  X=0, Y = 44.82 +/- 28.42 
  Weighted least-squares fit:  Y = 61.0 + 1.637 X  + -0.01665 X**2 

slope versus dZ, curvature < 5
  n = 49258 

  Weighted least-squares fit:  Y = 11.6 + 0.653 X  + -0.00001 X**2 
     at X = 100, Y = 76.8 
     effective RMSE xy = 119.2 

slope versus dZ, curvature < 15
  n = 181288 

  Weighted least-squares fit:  Y = 13.3 + 0.703 X  + -0.00039 X**2 

curvature versus dZ, slope < 10
  n = 8418 
  X=0, Y = 15.10 +/- 10.64 
  Weighted least-squares fit:  Y = 16.9 + 1.771 X  + -0.02310 X**2 


Number of samples 784621
Max dz = 900
Mean dz = 62
RMS dz = 88.5324799156
100cm = 81.1551054586 percentile value of dz