curvature versus slope
  n = 462817 
  X=0, Y = 34.55 +/- 20.31 
  Weighted least-squares fit:  Y = 42.8 + 2.289 X  + -0.02311 X**2 

slope versus dZ, curvature < 5
  n = 63696 

  Weighted least-squares fit:  Y = 9.3 + 0.287 X  + 0.00252 X**2 
     at X = 100, Y = 63.1 
     effective RMSE xy = 98.1 

slope versus dZ, curvature < 15
  n = 177000 

  Weighted least-squares fit:  Y = 9.8 + 0.312 X  + 0.00258 X**2 

curvature versus dZ, slope < 10
  n = 13052 
  X=0, Y = 12.60 +/- 7.93 
  Weighted least-squares fit:  Y = 11.2 + 1.317 X  + 0.09249 X**2 


Number of samples 466977
Max dz = 900
Mean dz = 39
RMS dz = 77.49838708
100cm = 91.1601642051 percentile value of dz