curvature versus slope
  n = 192302 
  X=0, Y = 42.58 +/- 22.26 
  Weighted least-squares fit:  Y = 55.4 + 2.297 X  + -0.02574 X**2 

slope versus dZ, curvature < 5
  n = 96645 

  Weighted least-squares fit:  Y = 10.2 + 0.661 X  + 0.00057 X**2 
     at X = 100, Y = 82.0 
     effective RMSE xy = 127.8 

slope versus dZ, curvature < 15
  n = 149114 

  Weighted least-squares fit:  Y = 9.4 + 0.752 X  + -0.00001 X**2 

curvature versus dZ, slope < 10
  n = 5217 
  X=0, Y = 17.57 +/- 9.61 
  Weighted least-squares fit:  Y = 18.3 + -1.525 X  + 0.97481 X**2 


Number of samples 193600
Max dz = 900
Mean dz = 47
RMS dz = 94.7734139936
100cm = 91.5976239669 percentile value of dz