curvature versus slope
  n = 436254 
  X=0, Y = 34.40 +/- 24.42 
  Weighted least-squares fit:  Y = 53.5 + 2.032 X  + -0.02025 X**2 

slope versus dZ, curvature < 5
  n = 6938 

  Weighted least-squares fit:  Y = 7.3 + 0.230 X  + 0.00020 X**2 
     at X = 100, Y = 32.3 
     effective RMSE xy = 49.4 

slope versus dZ, curvature < 15
  n = 37027 

  Weighted least-squares fit:  Y = 9.7 + 0.187 X  + 0.00113 X**2 

curvature versus dZ, slope < 10
  n = 2877 
  X=0, Y = 6.24 +/- 4.99 
  Weighted least-squares fit:  Y = 6.7 + 2.687 X  + -0.08752 X**2 


Number of samples 442666
Max dz = 900
Mean dz = 49
RMS dz = 75.9275970909
100cm = 85.9652650079 percentile value of dz