curvature versus slope
  n = 702503 
  X=0, Y = 45.89 +/- 22.59 
  Weighted least-squares fit:  Y = 43.4 + 0.938 X  + -0.00562 X**2 

slope versus dZ, curvature < 5
  n = 6361 

  Weighted least-squares fit:  Y = 4.9 + 0.084 X  + 0.00095 X**2 
     at X = 100, Y = 22.7 
     effective RMSE xy = 34.8 

slope versus dZ, curvature < 15
  n = 31097 

  Weighted least-squares fit:  Y = 5.3 + 0.053 X  + 0.00137 X**2 

curvature versus dZ, slope < 10
  n = 15317 
  X=0, Y = 5.97 +/- 3.29 
  Weighted least-squares fit:  Y = 5.3 + 0.160 X  + -0.00011 X**2 


Number of samples 703919
Max dz = 900
Mean dz = 14
RMS dz = 21.6564078277
100cm = 99.7570743225 percentile value of dz
Mean dz (curv<=5) = 8
RMS dz (curv<=5) = 11.7473401245