curvature versus slope
  n = 1108533 
  X=0, Y = 27.19 +/- 21.85 
  Weighted least-squares fit:  Y = 54.6 + 2.246 X  + -0.02354 X**2 

slope versus dZ, curvature < 5
  n = 125867 

  Weighted least-squares fit:  Y = 12.2 + -0.011 X  + 0.00275 X**2 
     at X = 100, Y = 38.5 
     effective RMSE xy = 57.4 

slope versus dZ, curvature < 15
  n = 370941 

  Weighted least-squares fit:  Y = 11.3 + 0.131 X  + 0.00189 X**2 

curvature versus dZ, slope < 10
  n = 98427 
  X=0, Y = 11.83 +/- 7.74 
  Weighted least-squares fit:  Y = 11.5 + 0.467 X  + 0.08391 X**2 


Number of samples 1129261
Max dz = 900
Mean dz = 30
RMS dz = 45.6289381862
100cm = 95.2711552068 percentile value of dz