curvature versus slope
  n = 135829 
  X=0, Y = 59.92 +/- 38.91 
  Weighted least-squares fit:  Y = 69.2 + 1.446 X  + -0.01486 X**2 

slope versus dZ, curvature < 5
  n = 9241 

  Weighted least-squares fit:  Y = 46.0 + 0.398 X  + -0.00207 X**2 
     at X = 100, Y = 65.1 
     effective RMSE xy = 72.2 

slope versus dZ, curvature < 15
  n = 21233 

  Weighted least-squares fit:  Y = 46.3 + 0.368 X  + -0.00062 X**2 

curvature versus dZ, slope < 10
  n = 2677 
  X=0, Y = 50.63 +/- 19.02 
  Weighted least-squares fit:  Y = 51.1 + -0.627 X  + 0.39294 X**2 


Number of samples 138075
Max dz = 900
Mean dz = 89
RMS dz = 133.296661624
100cm = 68.9893174 percentile value of dz