curvature versus slope
  n = 598001 
  X=0, Y = 38.66 +/- 28.12 
  Weighted least-squares fit:  Y = 58.2 + 1.907 X  + -0.02071 X**2 

slope versus dZ, curvature < 5
  n = 52896 

  Weighted least-squares fit:  Y = 14.4 + 0.258 X  + 0.00163 X**2 
     at X = 100, Y = 56.4 
     effective RMSE xy = 85.7 

slope versus dZ, curvature < 15
  n = 167411 

  Weighted least-squares fit:  Y = 13.6 + 0.378 X  + 0.00113 X**2 

curvature versus dZ, slope < 10
  n = 17023 
  X=0, Y = 18.23 +/- 10.31 
  Weighted least-squares fit:  Y = 16.3 + 1.940 X  + -0.06433 X**2 


Number of samples 605473
Max dz = 900
Mean dz = 51
RMS dz = 84.6286003665
100cm = 86.8889281603 percentile value of dz