curvature versus slope
  n = 836318 
  X=0, Y = 29.28 +/- 22.30 
  Weighted least-squares fit:  Y = 66.4 + 1.426 X  + -0.01414 X**2 

slope versus dZ, curvature < 5
  n = 20411 

  Weighted least-squares fit:  Y = 4.9 + 0.144 X  + 0.00072 X**2 
     at X = 100, Y = 26.4 
     effective RMSE xy = 40.8 

slope versus dZ, curvature < 15
  n = 60761 

  Weighted least-squares fit:  Y = 4.8 + 0.264 X  + -0.00007 X**2 

curvature versus dZ, slope < 10
  n = 6422 
  X=0, Y = 6.09 +/- 4.13 
  Weighted least-squares fit:  Y = 5.5 + 1.482 X  + 0.05079 X**2 


Number of samples 847129
Max dz = 700
Mean dz = 51
RMS dz = 76.5049018037
100cm = 84.6495634077 percentile value of dz