curvature versus slope
  n = 2066740 
  X=0, Y = 19.24 +/- 15.86 
  Weighted least-squares fit:  Y = 46.8 + 2.612 X  + -0.02794 X**2 

slope versus dZ, curvature < 5
  n = 93743 

  Weighted least-squares fit:  Y = 28.3 + 0.532 X  + -0.00196 X**2 
     at X = 100, Y = 61.8 
     effective RMSE xy = 86.3 

slope versus dZ, curvature < 15
  n = 371393 

  Weighted least-squares fit:  Y = 32.9 + 0.353 X  + -0.00039 X**2 

curvature versus dZ, slope < 10
  n = 48713 
  X=0, Y = 28.72 +/- 19.05 
  Weighted least-squares fit:  Y = 28.3 + 5.311 X  + -0.36893 X**2 


Number of samples 2088355
Max dz = 800
Mean dz = 56
RMS dz = 77.0194780559
100cm = 84.4660989152 percentile value of dz