curvature versus slope
  n = 193939 
  X=0, Y = 54.37 +/- 34.97 
  Weighted least-squares fit:  Y = 64.6 + 0.326 X  + -0.00020 X**2 

slope versus dZ, curvature < 5
  n = 1374 

  Weighted least-squares fit:  Y = 8.2 + 0.061 X  + 0.00055 X**2 
     at X = 100, Y = 19.8 
     effective RMSE xy = 28.3 

slope versus dZ, curvature < 15
  n = 5535 

  Weighted least-squares fit:  Y = 9.2 + 0.027 X  + 0.00100 X**2 

curvature versus dZ, slope < 10
  n = 2958 
  X=0, Y = 10.35 +/- 6.79 
  Weighted least-squares fit:  Y = 9.5 + 0.039 X  + -0.00187 X**2 


Number of samples 194280
Max dz = 900
Mean dz = 16
RMS dz = 21.8632111091
100cm = 99.7966851966 percentile value of dz
Mean dz (curv<=5) = 12
RMS dz (curv<=5) = 14.9666295471