curvature versus slope
  n = 1879948 
  X=0, Y = 31.04 +/- 18.40 
  Weighted least-squares fit:  Y = 51.9 + 2.287 X  + -0.02331 X**2 

slope versus dZ, curvature < 5
  n = 54737 

  Weighted least-squares fit:  Y = 6.5 + 0.261 X  + 0.00040 X**2 
     at X = 100, Y = 36.6 
     effective RMSE xy = 56.6 

slope versus dZ, curvature < 15
  n = 247865 

  Weighted least-squares fit:  Y = 7.6 + 0.244 X  + 0.00110 X**2 

curvature versus dZ, slope < 10
  n = 9013 
  X=0, Y = 8.80 +/- 5.71 
  Weighted least-squares fit:  Y = 9.3 + 0.332 X  + 0.17467 X**2 


Number of samples 1900425
Max dz = 800
Mean dz = 47
RMS dz = 71.379268699
100cm = 87.2142810161 percentile value of dz