curvature versus slope
  n = 259355 
  X=0, Y = 52.27 +/- 37.60 
  Weighted least-squares fit:  Y = 70.0 + 1.231 X  + -0.01274 X**2 

slope versus dZ, curvature < 5
  n = 3068 

  Weighted least-squares fit:  Y = 6.9 + 0.404 X  + 0.00024 X**2 
     at X = 100, Y = 49.6 
     effective RMSE xy = 77.2 

slope versus dZ, curvature < 15
  n = 13975 

  Weighted least-squares fit:  Y = 7.5 + 0.432 X  + 0.00048 X**2 

curvature versus dZ, slope < 10
  n = 2373 
  X=0, Y = 11.90 +/- 7.90 
  Weighted least-squares fit:  Y = 9.4 + 1.281 X  + 0.04372 X**2 


Number of samples 265147
Max dz = 800
Mean dz = 67
RMS dz = 93.7229961109
100cm = 76.2373324986 percentile value of dz