curvature versus slope
  n = 1330638 
  X=0, Y = 5.39 +/- 3.33 
  Weighted least-squares fit:  Y = 3.8 + 4.313 X  + -0.04486 X**2 

slope versus dZ, curvature < 5
  n = 878071 
  X=0, Y = 6.32 +/- 3.72 
  Weighted least-squares fit:  Y = 6.4 + 0.306 X  + -0.00122 X**2 
     at X = 100, Y = 24.8 
     effective RMSE xy = 37.7 

slope versus dZ, curvature < 15
  n = 1241329 
  X=0, Y = 6.56 +/- 3.94 
  Weighted least-squares fit:  Y = 6.4 + 0.357 X  + -0.00085 X**2 

curvature versus dZ, slope < 10
  n = 1176908 
  X=0, Y = 7.26 +/- 4.36 
  Weighted least-squares fit:  Y = 6.7 + 1.189 X  + 0.03646 X**2 


Number of samples 1331929
Max dz = 800
Mean dz = 7
RMS dz = 13.8564064606
100cm = 99.8911353383 percentile value of dz