curvature versus slope
  n = 2139985 
  X=0, Y = 16.10 +/- 12.75 
  Weighted least-squares fit:  Y = 45.7 + 2.905 X  + -0.03222 X**2 

slope versus dZ, curvature < 5
  n = 184443 

  Weighted least-squares fit:  Y = 69.4 + 0.296 X  + 0.00135 X**2 
     at X = 100, Y = 112.5 
     effective RMSE xy = 139.1 

slope versus dZ, curvature < 15
  n = 489141 

  Weighted least-squares fit:  Y = 71.2 + 0.326 X  + 0.00077 X**2 

curvature versus dZ, slope < 10
  n = 169061 
  X=0, Y = 68.21 +/- 37.87 
  Weighted least-squares fit:  Y = 67.8 + 3.182 X  + -0.06390 X**2 


Number of samples 2151002
Max dz = 900
Mean dz = 88
RMS dz = 112.008928216
100cm = 63.8911074932 percentile value of dz