curvature versus slope
  n = 491873 
  X=0, Y = 33.63 +/- 28.47 
  Weighted least-squares fit:  Y = 68.7 + 1.351 X  + -0.01441 X**2 

slope versus dZ, curvature < 5
  n = 24301 

  Weighted least-squares fit:  Y = 61.2 + 0.098 X  + 0.00182 X**2 
     at X = 100, Y = 89.2 
     effective RMSE xy = 101.9 

slope versus dZ, curvature < 15
  n = 63472 

  Weighted least-squares fit:  Y = 59.8 + 0.156 X  + 0.00161 X**2 

curvature versus dZ, slope < 10
  n = 13899 
  X=0, Y = 63.36 +/- 21.69 
  Weighted least-squares fit:  Y = 62.7 + -3.131 X  + 0.30491 X**2 


Number of samples 496834
Max dz = 900
Mean dz = 89
RMS dz = 124.414629365
100cm = 66.2297668839 percentile value of dz