curvature versus slope
  n = 8738568 
  X=0, Y = 35.02 +/- 15.59 
  Weighted least-squares fit:  Y = 29.0 + 0.734 X  + -0.00042 X**2 

slope versus dZ, curvature < 5
  n = 71027 

  Weighted least-squares fit:  Y = 5.6 + -0.078 X  + 0.00217 X**2 
     at X = 100, Y = 19.5 
     effective RMSE xy = 29.3 

slope versus dZ, curvature < 15
  n = 416699 

  Weighted least-squares fit:  Y = 7.0 + -0.113 X  + 0.00263 X**2 

curvature versus dZ, slope < 10
  n = 226856 
  X=0, Y = 3.42 +/- 2.32 
  Weighted least-squares fit:  Y = 5.8 + 0.091 X  + 0.00097 X**2 


Number of samples 8746352
Max dz = 900
Mean dz = 9
RMS dz = 14.4568322948
100cm = 99.8936013552 percentile value of dz
Mean dz (curv<=5) = 4
RMS dz (curv<=5) = 6.32455532034