curvature versus slope
  n = 422360 
  X=0, Y = 37.13 +/- 20.46 
  Weighted least-squares fit:  Y = 46.2 + 2.409 X  + -0.02583 X**2 

slope versus dZ, curvature < 5
  n = 91699 

  Weighted least-squares fit:  Y = 3.0 + 0.845 X  + -0.00334 X**2 
     at X = 100, Y = 54.1 
     effective RMSE xy = 84.9 

slope versus dZ, curvature < 15
  n = 215090 

  Weighted least-squares fit:  Y = 5.4 + 0.729 X  + -0.00211 X**2 

curvature versus dZ, slope < 10
  n = 11010 
  X=0, Y = 8.24 +/- 5.64 
  Weighted least-squares fit:  Y = 8.0 + 2.539 X  + -0.00715 X**2 


Number of samples 427212
Max dz = 900
Mean dz = 40
RMS dz = 75.3193202306
100cm = 91.0599421365 percentile value of dz