curvature versus slope
  n = 564131 
  X=0, Y = 12.87 +/- 11.05 
  Weighted least-squares fit:  Y = 17.7 + 4.114 X  + -0.04635 X**2 

slope versus dZ, curvature < 5
  n = 323175 
  X=0, Y = 12.42 +/- 8.90 
  Weighted least-squares fit:  Y = 9.2 + 0.483 X  + -0.00267 X**2 
     at X = 100, Y = 30.9 
     effective RMSE xy = 46.3 

slope versus dZ, curvature < 15
  n = 460969 
  X=0, Y = 12.39 +/- 8.57 
  Weighted least-squares fit:  Y = 9.1 + 0.473 X  + -0.00166 X**2 

curvature versus dZ, slope < 10
  n = 308416 
  X=0, Y = 11.68 +/- 7.79 
  Weighted least-squares fit:  Y = 10.4 + 1.382 X  + 0.02887 X**2 


Number of samples 573527
Max dz = 900
Mean dz = 17
RMS dz = 35.0713558335
100cm = 98.2049668106 percentile value of dz