curvature versus slope
  n = 351069 
  X=0, Y = 5.67 +/- 4.55 
  Weighted least-squares fit:  Y = 4.6 + 4.891 X  + -0.05369 X**2 

slope versus dZ, curvature < 5
  n = 258921 
  X=0, Y = 4.90 +/- 3.18 
  Weighted least-squares fit:  Y = 4.1 + 0.323 X  + -0.00135 X**2 
     at X = 100, Y = 22.8 
     effective RMSE xy = 35.3 

slope versus dZ, curvature < 15
  n = 328019 
  X=0, Y = 5.02 +/- 3.25 
  Weighted least-squares fit:  Y = 4.6 + 0.324 X  + 0.00030 X**2 

curvature versus dZ, slope < 10
  n = 306958 
  X=0, Y = 4.62 +/- 3.04 
  Weighted least-squares fit:  Y = 3.9 + 1.801 X  + 0.05306 X**2 


Number of samples 353011
Max dz = 900
Mean dz = 7
RMS dz = 24.7588368063
100cm = 99.4127661744 percentile value of dz