curvature versus slope
  n = 606701 
  X=0, Y = 18.69 +/- 15.10 
  Weighted least-squares fit:  Y = 46.9 + 2.611 X  + -0.02937 X**2 

slope versus dZ, curvature < 5
  n = 88883 

  Weighted least-squares fit:  Y = 9.1 + 0.497 X  + 0.00046 X**2 
     at X = 100, Y = 63.4 
     effective RMSE xy = 98.5 

slope versus dZ, curvature < 15
  n = 163362 

  Weighted least-squares fit:  Y = 9.2 + 0.574 X  + -0.00025 X**2 

curvature versus dZ, slope < 10
  n = 62123 
  X=0, Y = 11.60 +/- 7.98 
  Weighted least-squares fit:  Y = 11.8 + 1.676 X  + 0.08171 X**2 


Number of samples 614891
Max dz = 900
Mean dz = 50
RMS dz = 78.8733161468
100cm = 85.6207035068 percentile value of dz