curvature versus slope
  n = 497680 
  X=0, Y = 50.34 +/- 21.64 
  Weighted least-squares fit:  Y = 59.1 + 1.689 X  + -0.01679 X**2 

slope versus dZ, curvature < 5
  n = 27685 

  Weighted least-squares fit:  Y = 107.7 + 0.356 X  + 0.00044 X**2 
     at X = 100, Y = 147.8 
     effective RMSE xy = 158.9 

slope versus dZ, curvature < 15
  n = 125185 

  Weighted least-squares fit:  Y = 106.9 + 0.387 X  + 0.00028 X**2 

curvature versus dZ, slope < 10
  n = 429 
  X=0, Y = 110.05 +/- 60.31 
  Weighted least-squares fit:  Y = 110.1 + -0.114 X  + 0.10403 X**2 


Number of samples 499397
Max dz = 900
Mean dz = 124
RMS dz = 149.40883508
100cm = 37.6796416478 percentile value of dz
Mean dz (curv<=5) = 114
RMS dz (curv<=5) = 127.04723531