curvature versus slope
  n = 2773113 
  X=0, Y = 18.36 +/- 15.16 
  Weighted least-squares fit:  Y = 33.7 + 3.776 X  + -0.04178 X**2 

slope versus dZ, curvature < 5
  n = 469791 

  Weighted least-squares fit:  Y = 20.7 + 0.207 X  + -0.00227 X**2 
     at X = 100, Y = 18.7 
     Bad fit. P2 = 0
slope versus dZ, curvature < 15
  n = 864039 

  Weighted least-squares fit:  Y = 20.8 + 0.191 X  + 0.00044 X**2 

curvature versus dZ, slope < 10
  n = 539196 
  X=0, Y = 21.21 +/- 11.78 
  Weighted least-squares fit:  Y = 21.0 + 0.924 X  + -0.09753 X**2 


Number of samples 2791148
Max dz = 900
Mean dz = 46
RMS dz = 67.4536878162
100cm = 87.6029504706 percentile value of dz