curvature versus slope
  n = 501412 
  X=0, Y = 5.48 +/- 3.84 
  Weighted least-squares fit:  Y = 7.3 + 5.178 X  + -0.09541 X**2 

slope versus dZ, curvature < 5
  n = 341841 
  X=0, Y = 4.33 +/- 2.73 
  Weighted least-squares fit:  Y = 2.5 + 0.588 X  + -0.00191 X**2 
     at X = 100, Y = 42.2 
     effective RMSE xy = 66.1 

slope versus dZ, curvature < 15
  n = 386645 
  X=0, Y = 4.56 +/- 2.88 
  Weighted least-squares fit:  Y = 2.7 + 0.606 X  + -0.00151 X**2 

curvature versus dZ, slope < 10
  n = 361707 
  X=0, Y = 4.37 +/- 2.79 
  Weighted least-squares fit:  Y = 3.4 + 2.301 X  + -0.03128 X**2 


Number of samples 509865
Max dz = 400
Mean dz = 12
RMS dz = 26.3628526529
100cm = 98.0741961107 percentile value of dz