curvature versus slope
  n = 143554 
  X=0, Y = 28.88 +/- 24.73 
  Weighted least-squares fit:  Y = 51.5 + 2.572 X  + -0.02911 X**2 

slope versus dZ, curvature < 5
  n = 45097 

  Weighted least-squares fit:  Y = 28.0 + 0.436 X  + 0.00138 X**2 
     at X = 100, Y = 85.4 
     effective RMSE xy = 126.7 

slope versus dZ, curvature < 15
  n = 78753 

  Weighted least-squares fit:  Y = 29.1 + 0.417 X  + 0.00239 X**2 

curvature versus dZ, slope < 10
  n = 30375 
  X=0, Y = 29.25 +/- 19.18 
  Weighted least-squares fit:  Y = 30.6 + 2.859 X  + -0.05568 X**2 


Number of samples 145570
Max dz = 900
Mean dz = 65
RMS dz = 118.604384405
100cm = 82.3748025005 percentile value of dz
Mean dz (curv<=5) = 34
RMS dz (curv<=5) = 53.7494186015