curvature versus slope
  n = 156676 
  X=0, Y = 38.64 +/- 28.53 
  Weighted least-squares fit:  Y = 64.5 + 1.451 X  + -0.01524 X**2 

slope versus dZ, curvature < 5
  n = 7766 

  Weighted least-squares fit:  Y = 9.3 + 0.459 X  + 0.00094 X**2 
     at X = 100, Y = 64.6 
     effective RMSE xy = 100.3 

slope versus dZ, curvature < 15
  n = 23187 

  Weighted least-squares fit:  Y = 10.8 + 0.465 X  + 0.00100 X**2 

curvature versus dZ, slope < 10
  n = 3452 
  X=0, Y = 12.76 +/- 7.73 
  Weighted least-squares fit:  Y = 12.0 + 2.041 X  + 0.03873 X**2 


Number of samples 158006
Max dz = 900
Mean dz = 63
RMS dz = 104.403065089
100cm = 80.7399718998 percentile value of dz