curvature versus slope
  n = 316022 
  X=0, Y = 34.39 +/- 16.19 
  Weighted least-squares fit:  Y = 41.2 + 2.770 X  + -0.02989 X**2 

slope versus dZ, curvature < 5
  n = 80453 

  Weighted least-squares fit:  Y = 30.7 + 0.637 X  + -0.00035 X**2 
     at X = 100, Y = 90.9 
     effective RMSE xy = 134.4 

slope versus dZ, curvature < 15
  n = 180973 

  Weighted least-squares fit:  Y = 31.4 + 0.592 X  + 0.00026 X**2 

curvature versus dZ, slope < 10
  n = 5746 
  X=0, Y = 35.43 +/- 12.35 
  Weighted least-squares fit:  Y = 35.5 + 0.076 X  + -0.03180 X**2 


Number of samples 324699
Max dz = 900
Mean dz = 67
RMS dz = 97.4114982946
100cm = 86.2574261085 percentile value of dz