curvature versus slope
  n = 314316 
  X=0, Y = 82.14 +/- 27.07 
  Weighted least-squares fit:  Y = 81.8 + 0.529 X  + -0.00469 X**2 

slope versus dZ, curvature < 5
  n = 4030 

  Weighted least-squares fit:  Y = 9.2 + 0.661 X  + -0.00095 X**2 
     at X = 100, Y = 65.7 
     effective RMSE xy = 102.2 

slope versus dZ, curvature < 15
  n = 21725 

  Weighted least-squares fit:  Y = 15.9 + 0.496 X  + 0.00054 X**2 

curvature versus dZ, slope < 10
  n = 109 

  Weighted least-squares fit:  Y = 18.5 + 0.328 X  + 0.06097 X**2 


Number of samples 316641
Max dz = 900
Mean dz = 68
RMS dz = 106.780147968
100cm = 77.547127504 percentile value of dz