curvature versus slope
  n = 222075 
  X=0, Y = 25.20 +/- 19.05 
  Weighted least-squares fit:  Y = 49.6 + 2.295 X  + -0.02505 X**2 

slope versus dZ, curvature < 5
  n = 27932 

  Weighted least-squares fit:  Y = 13.7 + 0.074 X  + 0.00388 X**2 
     at X = 100, Y = 59.9 
     effective RMSE xy = 91.5 

slope versus dZ, curvature < 15
  n = 56627 

  Weighted least-squares fit:  Y = 13.1 + 0.210 X  + 0.00268 X**2 

curvature versus dZ, slope < 10
  n = 14463 
  X=0, Y = 14.99 +/- 8.98 
  Weighted least-squares fit:  Y = 14.1 + 1.501 X  + 0.01429 X**2 


Number of samples 226873
Max dz = 900
Mean dz = 54
RMS dz = 93.776329636
100cm = 84.1475186558 percentile value of dz