curvature versus slope
  n = 831471 
  X=0, Y = 22.59 +/- 18.68 
  Weighted least-squares fit:  Y = 42.1 + 3.044 X  + -0.03451 X**2 

slope versus dZ, curvature < 5
  n = 158642 

  Weighted least-squares fit:  Y = 44.8 + -0.238 X  + 0.00608 X**2 
     at X = 100, Y = 81.9 
     effective RMSE xy = 107.7 

slope versus dZ, curvature < 15
  n = 291389 

  Weighted least-squares fit:  Y = 42.4 + 0.006 X  + 0.00434 X**2 

curvature versus dZ, slope < 10
  n = 129971 
  X=0, Y = 43.72 +/- 21.71 
  Weighted least-squares fit:  Y = 44.2 + -0.703 X  + 0.12998 X**2 


Number of samples 850600
Max dz = 900
Mean dz = 67
RMS dz = 97.0257697728
100cm = 79.5182224312 percentile value of dz