curvature versus slope
  n = 736282 
  X=0, Y = 55.56 +/- 28.53 
  Weighted least-squares fit:  Y = 67.2 + 1.106 X  + -0.01027 X**2 

slope versus dZ, curvature < 5
  n = 26780 

  Weighted least-squares fit:  Y = 27.4 + 0.403 X  + 0.00211 X**2 
     at X = 100, Y = 88.8 
     effective RMSE xy = 132.7 

slope versus dZ, curvature < 15
  n = 129695 

  Weighted least-squares fit:  Y = 30.3 + 0.410 X  + 0.00207 X**2 

curvature versus dZ, slope < 10
  n = 1459 
  X=0, Y = 26.95 +/- 14.07 
  Weighted least-squares fit:  Y = 31.2 + 2.195 X  + -0.06653 X**2 


Number of samples 746587
Max dz = 900
Mean dz = 67
RMS dz = 90.9065454189
100cm = 77.0539803131 percentile value of dz
Mean dz (curv<=5) = 46
RMS dz (curv<=5) = 60.9425959408