curvature versus slope
  n = 4288900 
  X=0, Y = 5.12 +/- 2.86 
  Weighted least-squares fit:  Y = 2.2 + 3.570 X  + -0.03073 X**2 

slope versus dZ, curvature < 5
  n = 3004188 
  X=0, Y = 4.09 +/- 2.67 
  Weighted least-squares fit:  Y = 3.6 + 0.218 X  + -0.00169 X**2 
     at X = 100, Y = 8.5 
     effective RMSE xy = 12.0 

slope versus dZ, curvature < 15
  n = 4105315 
  X=0, Y = 4.31 +/- 2.82 
  Weighted least-squares fit:  Y = 3.9 + 0.217 X  + -0.00091 X**2 

curvature versus dZ, slope < 10
  n = 4078207 
  X=0, Y = 4.18 +/- 2.83 
  Weighted least-squares fit:  Y = 4.1 + 0.634 X  + 0.03354 X**2 


Number of samples 4289423
Max dz = 900
Mean dz = 4
RMS dz = 7.34846922835
100cm = 99.9880636626 percentile value of dz
Mean dz (curv<=5) = 3
RMS dz (curv<=5) = 5.0