curvature versus slope
  n = 315943 
  X=0, Y = 42.91 +/- 19.22 
  Weighted least-squares fit:  Y = 53.1 + 2.159 X  + -0.02370 X**2 

slope versus dZ, curvature < 5
  n = 131089 

  Weighted least-squares fit:  Y = 61.8 + -0.721 X  + 0.01055 X**2 
     at X = 100, Y = 95.2 
     effective RMSE xy = 113.7 

slope versus dZ, curvature < 15
  n = 200546 

  Weighted least-squares fit:  Y = 59.8 + -0.559 X  + 0.00951 X**2 

curvature versus dZ, slope < 10
  n = 7750 
  X=0, Y = 54.87 +/- 10.74 
  Weighted least-squares fit:  Y = 55.7 + -1.214 X  + 0.34218 X**2 


Number of samples 320352
Max dz = 900
Mean dz = 62
RMS dz = 85.0881895447
100cm = 82.4992508241 percentile value of dz