curvature versus slope
  n = 946254 
  X=0, Y = 30.24 +/- 28.20 
  Weighted least-squares fit:  Y = 29.3 + 3.554 X  + -0.03745 X**2 

slope versus dZ, curvature < 5
  n = 214410 

  Weighted least-squares fit:  Y = 13.6 + 0.118 X  + -0.00060 X**2 
     at X = 100, Y = 19.4 
     effective RMSE xy = 21.7 

slope versus dZ, curvature < 15
  n = 423264 

  Weighted least-squares fit:  Y = 13.7 + 0.192 X  + -0.00062 X**2 

curvature versus dZ, slope < 10
  n = 294192 
  X=0, Y = 17.00 +/- 9.97 
  Weighted least-squares fit:  Y = 14.0 + 1.065 X  + -0.03731 X**2 


Number of samples 968828
Max dz = 900
Mean dz = 29
RMS dz = 49.6890329952
100cm = 93.9951157481 percentile value of dz