curvature versus slope
  n = 576819 
  X=0, Y = 12.32 +/- 10.66 
  Weighted least-squares fit:  Y = 23.1 + 3.869 X  + -0.04381 X**2 

slope versus dZ, curvature < 5
  n = 221792 
  X=0, Y = 2.79 +/- 2.68 
  Weighted least-squares fit:  Y = 4.2 + 0.680 X  + -0.00195 X**2 
     at X = 100, Y = 52.7 
     effective RMSE xy = 82.5 

slope versus dZ, curvature < 15
  n = 356704 
  X=0, Y = 3.34 +/- 3.26 
  Weighted least-squares fit:  Y = 5.4 + 0.663 X  + -0.00201 X**2 

curvature versus dZ, slope < 10
  n = 199415 
  X=0, Y = 7.01 +/- 6.07 
  Weighted least-squares fit:  Y = 6.7 + 2.848 X  + 0.01043 X**2 


Number of samples 588454
Max dz = 900
Mean dz = 24
RMS dz = 49.4974746831
100cm = 95.7002586438 percentile value of dz