curvature versus slope
  n = 2896228 
  X=0, Y = 36.63 +/- 22.36 
  Weighted least-squares fit:  Y = 42.4 + 2.293 X  + -0.02127 X**2 

slope versus dZ, curvature < 5
  n = 133362 

  Weighted least-squares fit:  Y = 6.5 + 0.436 X  + -0.00239 X**2 
     at X = 100, Y = 26.2 
     effective RMSE xy = 39.8 

slope versus dZ, curvature < 15
  n = 678778 

  Weighted least-squares fit:  Y = 9.1 + 0.426 X  + -0.00181 X**2 

curvature versus dZ, slope < 10
  n = 26565 
  X=0, Y = 8.13 +/- 5.40 
  Weighted least-squares fit:  Y = 7.8 + 2.391 X  + -0.05228 X**2 


Number of samples 2920303
Max dz = 800
Mean dz = 31
RMS dz = 65.0615093585
100cm = 94.9059395549 percentile value of dz