curvature versus slope
  n = 567924 
  X=0, Y = 47.73 +/- 34.10 
  Weighted least-squares fit:  Y = 76.6 + 0.861 X  + -0.00744 X**2 

slope versus dZ, curvature < 5
  n = 4676 

  Weighted least-squares fit:  Y = 70.0 + 0.259 X  + -0.00092 X**2 
     at X = 100, Y = 86.7 
     effective RMSE xy = 80.3 

slope versus dZ, curvature < 15
  n = 25096 

  Weighted least-squares fit:  Y = 73.9 + 0.126 X  + 0.00102 X**2 

curvature versus dZ, slope < 10
  n = 1073 
  X=0, Y = 70.43 +/- 38.17 
  Weighted least-squares fit:  Y = 72.5 + 0.890 X  + -0.00443 X**2 


Number of samples 572294
Max dz = 900
Mean dz = 89
RMS dz = 117.652029307
100cm = 62.5255550469 percentile value of dz
Mean dz (curv<=5) = 68
RMS dz (curv<=5) = 85.375640554