curvature versus slope
  n = 658666 
  X=0, Y = 54.02 +/- 26.07 
  Weighted least-squares fit:  Y = 59.1 + 1.830 X  + -0.01974 X**2 

slope versus dZ, curvature < 5
  n = 116994 

  Weighted least-squares fit:  Y = 22.4 + 0.511 X  + 0.00083 X**2 
     at X = 100, Y = 81.8 
     effective RMSE xy = 123.6 

slope versus dZ, curvature < 15
  n = 308338 

  Weighted least-squares fit:  Y = 23.2 + 0.546 X  + 0.00069 X**2 

curvature versus dZ, slope < 10
  n = 3611 
  X=0, Y = 28.27 +/- 16.69 
  Weighted least-squares fit:  Y = 34.4 + -4.319 X  + 0.61580 X**2 


Number of samples 673497
Max dz = 900
Mean dz = 63
RMS dz = 89.8776946745
100cm = 82.1576042655 percentile value of dz