curvature versus slope
  n = 318161 
  X=0, Y = 50.43 +/- 37.86 
  Weighted least-squares fit:  Y = 82.3 + 0.694 X  + -0.00686 X**2 

slope versus dZ, curvature < 5
  n = 4395 

  Weighted least-squares fit:  Y = 70.8 + -0.208 X  + 0.00342 X**2 
     at X = 100, Y = 84.2 
     effective RMSE xy = 71.6 

slope versus dZ, curvature < 15
  n = 16649 

  Weighted least-squares fit:  Y = 68.8 + -0.088 X  + 0.00277 X**2 

curvature versus dZ, slope < 10
  n = 878 
  X=0, Y = 72.53 +/- 13.71 
  Weighted least-squares fit:  Y = 71.5 + -1.171 X  + 0.29950 X**2 


Number of samples 323646
Max dz = 900
Mean dz = 101
RMS dz = 131.863565855
100cm = 60.0761325646 percentile value of dz