curvature versus slope
  n = 508856 
  X=0, Y = 18.34 +/- 15.48 
  Weighted least-squares fit:  Y = 44.4 + 2.468 X  + -0.02556 X**2 

slope versus dZ, curvature < 5
  n = 36355 

  Weighted least-squares fit:  Y = 8.5 + 0.246 X  + 0.00039 X**2 
     at X = 100, Y = 37.0 
     effective RMSE xy = 56.6 

slope versus dZ, curvature < 15
  n = 82677 

  Weighted least-squares fit:  Y = 9.0 + 0.287 X  + 0.00028 X**2 

curvature versus dZ, slope < 10
  n = 28297 
  X=0, Y = 9.50 +/- 6.05 
  Weighted least-squares fit:  Y = 8.7 + 2.184 X  + -0.07100 X**2 


Number of samples 517009
Max dz = 900
Mean dz = 38
RMS dz = 59.160797831
100cm = 92.0252838925 percentile value of dz