curvature versus slope
  n = 803530 
  X=0, Y = 34.87 +/- 21.60 
  Weighted least-squares fit:  Y = 52.0 + 2.092 X  + -0.02282 X**2 

slope versus dZ, curvature < 5
  n = 70069 

  Weighted least-squares fit:  Y = 10.6 + 0.456 X  + 0.00189 X**2 
     at X = 100, Y = 75.0 
     effective RMSE xy = 116.7 

slope versus dZ, curvature < 15
  n = 184804 

  Weighted least-squares fit:  Y = 10.6 + 0.548 X  + 0.00088 X**2 

curvature versus dZ, slope < 10
  n = 17963 
  X=0, Y = 15.51 +/- 7.68 
  Weighted least-squares fit:  Y = 11.4 + 4.073 X  + -0.09100 X**2 


Number of samples 820126
Max dz = 900
Mean dz = 62
RMS dz = 89.5153618101
100cm = 79.5738703565 percentile value of dz