curvature versus slope
  n = 148499 
  X=0, Y = 30.81 +/- 18.19 
  Weighted least-squares fit:  Y = 49.5 + 2.354 X  + -0.02522 X**2 

slope versus dZ, curvature < 5
  n = 15937 

  Weighted least-squares fit:  Y = 16.4 + -0.374 X  + 0.00942 X**2 
     at X = 100, Y = 73.2 
     effective RMSE xy = 112.1 

slope versus dZ, curvature < 15
  n = 39529 

  Weighted least-squares fit:  Y = 15.5 + -0.303 X  + 0.01023 X**2 

curvature versus dZ, slope < 10
  n = 3830 
  X=0, Y = 15.62 +/- 10.77 
  Weighted least-squares fit:  Y = 14.8 + -0.460 X  + 0.17875 X**2 


Number of samples 150750
Max dz = 900
Mean dz = 82
RMS dz = 140.573824021
100cm = 71.8567164179 percentile value of dz