curvature versus slope
  n = 2584678 
  X=0, Y = 20.79 +/- 15.01 
  Weighted least-squares fit:  Y = 63.7 + 1.845 X  + -0.02012 X**2 

slope versus dZ, curvature < 5
  n = 78062 

  Weighted least-squares fit:  Y = 15.4 + 0.087 X  + 0.00298 X**2 
     at X = 100, Y = 53.9 
     effective RMSE xy = 81.2 

slope versus dZ, curvature < 15
  n = 229891 

  Weighted least-squares fit:  Y = 13.1 + 0.311 X  + 0.00139 X**2 

curvature versus dZ, slope < 10
  n = 25412 
  X=0, Y = 16.85 +/- 11.66 
  Weighted least-squares fit:  Y = 18.1 + -0.085 X  + 0.22226 X**2 


Number of samples 2597195
Max dz = 900
Mean dz = 52
RMS dz = 71.8957578721
100cm = 85.3750295992 percentile value of dz