curvature versus slope
  n = 1120489 
  X=0, Y = 27.45 +/- 17.79 
  Weighted least-squares fit:  Y = 54.2 + 2.036 X  + -0.02160 X**2 

slope versus dZ, curvature < 5
  n = 47766 

  Weighted least-squares fit:  Y = 11.2 + 0.360 X  + 0.00187 X**2 
     at X = 100, Y = 65.9 
     effective RMSE xy = 101.9 

slope versus dZ, curvature < 15
  n = 150469 

  Weighted least-squares fit:  Y = 11.0 + 0.454 X  + 0.00129 X**2 

curvature versus dZ, slope < 10
  n = 11611 
  X=0, Y = 13.76 +/- 7.93 
  Weighted least-squares fit:  Y = 13.5 + 1.231 X  + 0.08589 X**2 


Number of samples 1137326
Max dz = 900
Mean dz = 59
RMS dz = 88.3006228744
100cm = 80.9722102546 percentile value of dz