curvature versus slope
  n = 297163 
  X=0, Y = 53.53 +/- 29.67 
  Weighted least-squares fit:  Y = 67.8 + 1.428 X  + -0.01554 X**2 

slope versus dZ, curvature < 5
  n = 23849 

  Weighted least-squares fit:  Y = 18.9 + -0.069 X  + 0.00701 X**2 
     at X = 100, Y = 82.1 
     effective RMSE xy = 125.5 

slope versus dZ, curvature < 15
  n = 77687 

  Weighted least-squares fit:  Y = 19.0 + 0.009 X  + 0.00625 X**2 

curvature versus dZ, slope < 10
  n = 1887 
  X=0, Y = 18.09 +/- 6.25 
  Weighted least-squares fit:  Y = 17.0 + 1.800 X  + 0.00194 X**2 


Number of samples 300016
Max dz = 900
Mean dz = 64
RMS dz = 109.539947051
100cm = 80.1570582902 percentile value of dz