curvature versus slope
  n = 3150444 
  X=0, Y = 40.52 +/- 25.86 
  Weighted least-squares fit:  Y = 61.9 + 1.768 X  + -0.01876 X**2 

slope versus dZ, curvature < 5
  n = 114589 

  Weighted least-squares fit:  Y = 14.6 + 0.080 X  + 0.00105 X**2 
     at X = 100, Y = 33.1 
     effective RMSE xy = 46.7 

slope versus dZ, curvature < 15
  n = 697531 

  Weighted least-squares fit:  Y = 15.1 + 0.096 X  + 0.00112 X**2 

curvature versus dZ, slope < 10
  n = 8164 
  X=0, Y = 14.60 +/- 10.02 
  Weighted least-squares fit:  Y = 14.5 + 0.461 X  + 0.20511 X**2 


Number of samples 3209867
Max dz = 900
Mean dz = 36
RMS dz = 52.8677595515
100cm = 93.2785377089 percentile value of dz