curvature versus slope
  n = 312395 
  X=0, Y = 31.43 +/- 15.86 
  Weighted least-squares fit:  Y = 44.7 + 2.509 X  + -0.02700 X**2 

slope versus dZ, curvature < 5
  n = 70036 

  Weighted least-squares fit:  Y = 11.3 + -0.085 X  + 0.00604 X**2 
     at X = 100, Y = 63.2 
     effective RMSE xy = 97.7 

slope versus dZ, curvature < 15
  n = 121117 

  Weighted least-squares fit:  Y = 10.7 + 0.007 X  + 0.00536 X**2 

curvature versus dZ, slope < 10
  n = 10628 
  X=0, Y = 10.25 +/- 5.74 
  Weighted least-squares fit:  Y = 9.5 + 1.215 X  + 0.04873 X**2 


Number of samples 321181
Max dz = 900
Mean dz = 48
RMS dz = 84.9470423264
100cm = 84.8767517381 percentile value of dz